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Number Theory problems
Problem Name Online Judge Year Contest Difficulty Level
1 Factorial Categories SPOJ 1
2 Prime or Not Categories SPOJ 1
3 Again Twenty Five! Categories Codeforces Experimental Educational Round: VolBIT Formulas Blitz 1
4 The Equation Categories SGU 1
5 Alyona and Numbers Categories Codeforces Codeforces Round #358 (Div. 2) 1
6 Lucky Division Categories Codeforces Codeforces Beta Round #91 (Div. 2 Only) 1
7 Two squares or not two squares Categories SPOJ 1
8 Fombinatorial Categories CodeChef 1
9 Simply Emirp Categories UVA 1
10 Bear and Poker Categories Codeforces Codeforces Round #318 [RussianCodeCup Thanks-Round] (Div. 1) & Codeforces Round #318 [RussianCodeCup Thanks-Round] (Div. 2) 1
11 A and B and Team Training Categories Codeforces Codeforces Round #294 (Div. 2) 1
12 Euler Totient Function Categories SPOJ 1
13 Graph Connectivity Categories UVA 1
14 Panoramix's Prediction Categories Codeforces Codeforces Beta Round #69 (Div. 2 Only) 1
15 Fedya and Maths Categories Codeforces Codeforces Round #260 (Div. 2) 1
16 The primary problem Categories UVA 1
17 Cifera Categories Codeforces Codeforces Beta Round #86 (Div. 2 Only) 1
18 Marbles Categories SPOJ 1
19 Tip Top Game Categories SPOJ 1
20 Factors and Factorials Categories UVA 1
21 Almost Prime Numbers Categories UVA 1
22 Toy Army Categories Codeforces Codeforces Beta Round #72 (Div. 2 Only) 1
23 Divisors Categories SPOJ 1
24 Goldbach's Conjecture (II) Categories UVA 1
25 Design Tutorial: Learn from Math Categories Codeforces Codeforces Round #270 1
26 Ilya and Bank Account Categories Codeforces Codeforces Round #186 (Div. 2) 1
27 Integer Factorization (15 digits) Categories SPOJ 1
28 String Task Categories Codeforces Codeforces Beta Round #89 (Div. 2) 1
29 Prime Words Categories UVA 1
30 Medium Factorization Categories SPOJ 1
31 Count the factors Categories TJU 1
32 Game of Lines Categories SPOJ 1
33 T-primes Categories Codeforces Codeforces Round #142 (Div. 2) 1
34 Arpa’s hard exam and Mehrdad’s naive cheat Categories Codeforces Codeforces Round #383 (Div. 2) 1
35 Totient Extreme Categories SPOJ 1
36 Vasya and Petya's Game Categories Codeforces Codeforces Round #319 (Div. 1) & Codeforces Round #319 (Div. 2) 1
37 Relatives Categories UVA 1
38 Goldbach's Conjecture Categories UVA 1
39 Factovisors Categories UVA 1
40 Twin Primes Categories UVA 1
41 Hexadecimal's theorem Categories Codeforces Codeforces Round #125 (Div. 2) 1
42 Bachgold Problem Categories Codeforces Codeforces Round #388 (Div. 2) 1
43 Celebrity jeopardy Categories UVA 1
44 Prime Generator Categories SPOJ 1
45 Play with Floor and Ceil Categories UVA 1
46 Almost Prime Categories Codeforces Codeforces Beta Round #26 (Codeforces format) 1
47 Multiplication Table Categories Codeforces Codeforces Round #319 (Div. 2) 1
48 LCM Sum Categories SPOJ 1
49 Prime Number Theorem Categories SPOJ 1
50 Ones Categories UVA 1
51 Prime Cuts Categories UVA 1
52 The Moronic Cowmpouter Categories SPOJ 1
53 Factorial Categories Live Archive 2000 Europe - Central 1
54 GCD Extreme Categories SPOJ 1
55 Divisor Summation Categories SPOJ 1
56 Drazil and His Happy Friends Categories Codeforces Codeforces Round #292 (Div. 1) & Codeforces Round #292 (Div. 2) & Codeforces Round #292 (Div. 1) & Codeforces Round #292 (Div. 2) 2
57 k-th divisor Categories Codeforces Educational Codeforces Round 17 2
58 Psycho Categories SPOJ 2
59 Mr. Azad and his Son!!!!! Categories UVA 2
60 Anagrammatic Primes Categories UVA 2
61 Square-free integers Categories SPOJ 2
62 Equation Categories SPOJ 2
63 Marbles Categories UVA 2
64 Minimum Number Categories SPOJ 2
65 Divisors 2 Categories SPOJ 2
66 Pythagorean Triples Categories Codeforces Codeforces Round #368 (Div. 2) 2
67 Jumping Champion Categories UVA 2
68 Ice Sculptures Categories Codeforces VK Cup 2012 Qualification Round 1 2
69 TEX Quotes Categories Live Archive 1994 North America - East Central NA 2
70 Integer Factorization (20 digits) Categories SPOJ 2
71 N DIV PHI_N Categories SPOJ 2
72 Dima and Lisa Categories Codeforces Codeforces Round #324 (Div. 2) 2
73 Pride Categories Codeforces Codeforces Round #446 (Div. 1) & Codeforces Round #446 (Div. 2) 2
74 Vladik and fractions Categories Codeforces Codeforces Round #384 (Div. 2) 2
75 Odd Numbers of Divisors Categories SPOJ 2
76 Mint Categories UVA 2
77 Prime Again Categories SPOJ 2
78 Prime Matrix Categories Codeforces Codeforces Round #166 (Div. 2) 2
79 Taxes Categories Codeforces Codeforces Round #382 (Div. 2) & Codeforces Round #382 (Div. 1) 2
80 MCQ Exam Categories A2 Online Judge 2
81 Primitive Root Categories SPOJ 2
82 Rational Resistance Categories Codeforces Codeforces Round #200 (Div. 1) & Codeforces Round #200 (Div. 2) 2
83 Playing with Marbles Categories SPOJ 2
84 The Bytelandian Cryptographer (Act I) Categories SPOJ 2
85 Mashmokh and Numbers Categories Codeforces Codeforces Round #240 (Div. 1) & Codeforces Round #240 (Div. 2) 2
86 Divisor Summation (Hard) Categories SPOJ 2
87 Number Theory for Newbies Categories UVA 2
88 Leha and Function Categories Codeforces Codeforces Round #429 (Div. 1) & Codeforces Round #429 (Div. 2) 2
89 Sort fractions Categories SPOJ 2
90 LCM Challenge Categories Codeforces Codeforces Round #146 (Div. 1) & Codeforces Round #146 (Div. 2) 2
91 Alice and Bob Categories Codeforces Codeforces Round #201 (Div. 1) & Codeforces Round #201 (Div. 2) 2
92 Soldier and Number Game Categories Codeforces Codeforces Round #304 (Div. 2) 2
93 Arpa’s obvious problem and Mehrdad’s terrible solution Categories Codeforces Codeforces Round #383 (Div. 2) 2
94 Goldbach and Euler Categories UVA 2
95 Permutation Primes Categories Live Archive 2004 Asia - Dhaka 3
96 Homework Categories SPOJ 3
97 Good Sequences Categories Codeforces Codeforces Round #162 (Div. 1) & Codeforces Round #162 (Div. 2) 3
98 GCD Determinant Categories SPOJ 3
99 The Meaningless Game Categories Codeforces Codeforces Round #426 (Div. 1) & Codeforces Round #426 (Div. 2) 3
100 DDF Categories UVA 3
101 Primal Fear Categories SPOJ 3
102 Easy Number Challenge Categories Codeforces Codeforces Round #146 (Div. 2) 3
103 Chef and Functions Categories CodeChef 3
104 Eugeny and Play List Categories Codeforces Codeforces Round #182 (Div. 2) 3
105 Congruence Equation Categories SPOJ 3
106 Skyscraper Floors Categories SPOJ 3
107 Fox Dividing Cheese Categories Codeforces Codeforces Round #218 (Div. 2) 3
108 Noldbach problem Categories Codeforces Codeforces Beta Round #17 3
109 Primes on Interval Categories Codeforces Codeforces Round #147 (Div. 2) 3
110 A Trivial Problem Categories Codeforces Manthan, Codefest 16 3
111 Sky Code Categories SPOJ 3
112 Little Elephant and Numbers Categories Codeforces Codeforces Round #136 (Div. 2) 3
113 Mike and gcd problem Categories Codeforces Codeforces Round #410 (Div. 2) 3
114 Modified GCD Categories Codeforces Codeforces Beta Round #67 (Div. 2) 3
115 Win or Freeze Categories Codeforces Codeforces Round #107 (Div. 1) & Codeforces Round #107 (Div. 2) 3
116 Bear and Prime Numbers Categories Codeforces Codeforces Round #226 (Div. 2) 3
117 The Super Powers Categories UVA 3
118 Binomial Coefficients Categories SPOJ 3
119 Cows and Primitive Roots Categories Codeforces Codeforces Round #174 (Div. 2) 3
120 Levko and Permutation Categories Codeforces Codeforces Round #210 (Div. 2) 3
121 Routine Problem Categories Codeforces Codeforces Round #196 (Div. 2) 3
122 Primes or Palindromes? Categories Codeforces Codeforces Round #315 (Div. 1) & Codeforces Round #315 (Div. 2) 3
123 Quiz Categories Codeforces Codeforces Round #196 (Div. 2) & Codeforces Round #196 (Div. 1) 3
124 Colliders Categories Codeforces Codeforces Round #109 (Div. 1) & Codeforces Round #109 (Div. 2) 4
125 Broken Keyboard Categories UVA 4
126 Well-known Numbers Categories Codeforces Codeforces Round #139 (Div. 2) 4
127 Devu and Partitioning of the Array Categories Codeforces Codeforces Round #251 (Div. 2) 4
128 Round Table Knights Categories Codeforces Codeforces Beta Round #65 (Div. 2) 4
129 N DIV PHI_N (Hard) Categories SPOJ 4
130 Find Maximum Categories Codeforces Codeforces Round #205 (Div. 2) 4
131 Subtractions Categories Codeforces Codeforces Testing Round #5 4
132 Subtraction Categories A2 Online Judge 4
133 Multipliers Categories Codeforces Codeforces Round #338 (Div. 2) 4
134 Boring Card Game Categories Live Archive 2011 Europe - Central 4
135 Ralph And His Magic Field Categories Codeforces Codeforces Round #447 (Div. 2) 4
136 Fortune Telling Categories Codeforces Codeforces Beta Round #55 (Div. 2) 4
137 Petya and Divisors Categories Codeforces Codeforces Beta Round #85 (Div. 1 Only) & Codeforces Beta Round #85 (Div. 2 Only) 4
138 Gerald and Giant Chess Categories Codeforces Codeforces Round #313 (Div. 1) & Codeforces Round #313 (Div. 2) 4
139 Divisible by Seven Categories Codeforces Codeforces Round #221 (Div. 1) & Codeforces Round #221 (Div. 2) 4
140 Chilly Willy Categories Codeforces Codeforces Round #152 (Div. 2) 4
141 Gaussian Prime Factors Categories Live Archive 2006 Asia - Manila 4
142 SETI Categories SPOJ 4
143 Ant colony Categories Codeforces Codeforces Round #271 (Div. 2) 4
144 Rank of a Fraction Categories SPOJ 4
145 Fox And Jumping Categories Codeforces Codeforces Round #290 (Div. 2) & Codeforces Round #290 (Div. 1) 4
146 Dots Categories SPOJ 4
147 Ksusha and Array Categories Codeforces Croc Champ 2013 - Round 2 (Div. 2 Edition) 4
148 Skyscraper Floors Categories UVA 4
149 Remainders Game Categories Codeforces Codeforces Round #360 (Div. 1) & Codeforces Round #360 (Div. 2) 4
150 Irrational problem Categories Codeforces Codeforces Beta Round #62 4
151 Winter is here Categories Codeforces Codeforces Round #428 (Div. 2) 5
152 Number With The Given Amount Of Divisors Categories Codeforces Codeforces Beta Round #27 (Codeforces format, Div. 2) 5
153 Mike and Foam Categories Codeforces Codeforces Round #305 (Div. 1) & Codeforces Round #305 (Div. 2) 5
154 Chocolate Categories Codeforces Codeforces Round #279 (Div. 2) 5
155 Rectangular Game Categories Codeforces ABBYY Cup 2.0 - Easy 5
156 Monitor Categories Codeforces Codeforces Beta Round #16 (Div. 2 Only) 5
157 Moodular Arithmetic Categories Codeforces Codeforces Round #334 (Div. 1) & Codeforces Round #334 (Div. 2) 5
158 Palindrome Degree Categories Codeforces Codeforces Beta Round #7 5
159 Array and Operations Categories Codeforces Codeforces Round #284 (Div. 1) & Codeforces Round #284 (Div. 2) 5
160 Prime Permutation Categories Codeforces Codeforces Beta Round #92 (Div. 1 Only) & Codeforces Beta Round #92 (Div. 2 Only) 5
161 Shaass and Lights Categories Codeforces Codeforces Round #178 (Div. 2) 5
162 Pseudorandom Sequence Period Categories Codeforces Croc Champ 2012 - Qualification Round 5
163 Roman and Numbers Categories Codeforces Codeforces Round #235 (Div. 2) 5
164 Vasya and Beautiful Arrays Categories Codeforces Codeforces Round #206 (Div. 1) & Codeforces Round #206 (Div. 2) 5
165 Upgrading Array Categories Codeforces Codeforces Round #236 (Div. 2) & Codeforces Round #236 (Div. 1) 5
166 Vasily the Bear and Sequence Categories Codeforces Codeforces Round #195 (Div. 2) 5
167 Petya and His Friends Categories Codeforces Codeforces Beta Round #61 (Div. 2) 5
168 Line Categories Codeforces Codeforces Beta Round #7 5
169 Clique in the Divisibility Graph Categories Codeforces VK Cup 2015 - Finals, online mirror 5
170 Anton and School - 2 Categories Codeforces Codeforces Round #404 (Div. 2) 5
171 Tutorial BFS Categories SPOJ 5
172 Rectangular Game Categories Codeforces ABBYY Cup 2.0 - Easy 5
173 Beaver Game Categories Codeforces Codeforces Beta Round #70 (Div. 2) 6
174 Devu and Flowers Categories Codeforces Codeforces Round #258 (Div. 2) 6
175 Apple Tree Categories Codeforces Codeforces Round #202 (Div. 1) & Codeforces Round #202 (Div. 2) 6
176 Beautiful numbers Categories Codeforces Codeforces Beta Round #51 6
177 Polygon Encoder Categories SPOJ 6
178 Longest Subsequence Categories Codeforces Educational Codeforces Round 9 6
179 Unusual Sequences Categories Codeforces Codeforces Round #450 (Div. 2) 6
180 GukiZ and Binary Operations Categories Codeforces Codeforces Round #307 (Div. 2) 6
181 DZY Loves Fibonacci Numbers Categories Codeforces Codeforces Round #255 (Div. 1) & Codeforces Round #255 (Div. 2) 6
182 Bots Categories Codeforces Bubble Cup 8 - Finals [Online Mirror] 6
183 Pluses everywhere Categories Codeforces Codeforces Round #295 (Div. 2) & Codeforces Round #295 (Div. 1) 6
184 Printing some primes (Hard) Categories SPOJ 6
185 Divisors Categories Codeforces Codeforces Round #256 (Div. 2) 6
186 Lucky Permutation Categories Codeforces Codeforces Beta Round #91 (Div. 1 Only) & Codeforces Beta Round #91 (Div. 2 Only) 6
187 Goldbach++ Categories Live Archive 2005 North America - Southeast USA 6
188 Calendar Reform Categories Codeforces Croc Champ 2012 - Qualification Round 6
189 Jzzhu and Apples Categories Codeforces Codeforces Round #257 (Div. 1) & Codeforces Round #257 (Div. 2) 6
190 ZS and The Birthday Paradox Categories Codeforces Codeforces Round #369 (Div. 2) 6
191 Array GCD Categories Codeforces AIM Tech Round (Div. 1) & AIM Tech Round (Div. 2) 6
192 Reducing Fractions Categories Codeforces Codeforces Round #137 (Div. 2) 6
193 Prefix Product Sequence Categories Codeforces Codeforces Round #278 (Div. 1) & Codeforces Round #278 (Div. 2) 6
194 Very Interesting Game Categories Codeforces Codeforces Beta Round #88 6
195 On Number of Decompositions into Multipliers Categories Codeforces Codeforces Round #232 (Div. 1) & Codeforces Round #232 (Div. 2) 7
196 Divisor Tree Categories Codeforces Codeforces Round #196 (Div. 2) & Codeforces Round #196 (Div. 1) 7
197 On Sum of Fractions Categories Codeforces Codeforces Round #232 (Div. 1) & Codeforces Round #232 (Div. 2) 7
198 Finding the Kth Prime (Hard) Categories SPOJ 7
199 Alice, Bob, Oranges and Apples Categories Codeforces Codeforces Round #325 (Div. 1) & Codeforces Round #325 (Div. 2) 7
200 Traffic Jams in the Land Categories Codeforces Codeforces Round #284 (Div. 1) 7
201 Chessboard Billiard Categories Codeforces Codeforces Beta Round #68 7
202 Pairs of Numbers Categories Codeforces Codeforces Testing Round #3 7
203 Sum of Remainders Categories Codeforces Educational Codeforces Round 5 7
204 Double Happiness Categories Codeforces Codeforces Beta Round #86 (Div. 1 Only) & Codeforces Beta Round #86 (Div. 2 Only) 7
205 Integer Factorization (29 digits) Categories SPOJ 7
206 ucyhf Categories Codeforces April Fools Day Contest 7
207 Number Transformation Categories Codeforces Codeforces Round #153 (Div. 1) & Codeforces Round #153 (Div. 2) 7
208 Bamboo Partition Categories Codeforces Codeforces Round #424 (Div. 1, rated, based on VK Cup Finals) & Codeforces Round #424 (Div. 2, rated, based on VK Cup Finals) 7
209 Digital Root Categories Codeforces Codeforces Beta Round #10 7
210 Number Challenge Categories Codeforces Codeforces Round #146 (Div. 1) 8
211 Superior Periodic Subarrays Categories Codeforces Codeforces Round #323 (Div. 1) & Codeforces Round #323 (Div. 2) 8
212 Beautiful Set Categories Codeforces Codeforces Round #213 (Div. 1) & Codeforces Round #213 (Div. 2) 8
213 Ada and Connections Categories SPOJ 8
214 Cube Problem Categories Codeforces Croc Champ 2013 - Round 2 8
215 Periodical Numbers Categories Codeforces Codeforces Round #132 (Div. 2) 8
216 Numbers Categories Codeforces Codeforces Beta Round #72 (Div. 1 Only) 8
217 Prime Problem Categories Codeforces School Team Contest #3 (Winter Computer School 2010/11) 8
218 Unsolvable Categories Codeforces Codeforces Round #139 (Div. 2) 8
219 Anniversary Categories Codeforces Codeforces Round #140 (Div. 1) & Codeforces Round #140 (Div. 2) 8
220 Ultimate Weirdness of an Array Categories Codeforces Codeforces Round #352 (Div. 1) & Codeforces Round #352 (Div. 2) 8
221 GCD Table Categories Codeforces Codeforces Round #196 (Div. 1) 8
222 Martian Luck Categories Codeforces Codeforces Round #133 (Div. 2) 8
223 Mishka and Divisors Categories Codeforces Codeforces Round #365 (Div. 2) 8
224 Notepad Categories Codeforces Codeforces Beta Round #17 8
225 Timofey and remoduling Categories Codeforces Codeforces Round #395 (Div. 1) & Codeforces Round #395 (Div. 2) 8
226 Cowslip Collections Categories Codeforces CROC 2016 - Elimination Round 8
227 Three Horses Categories Codeforces Codeforces Round #166 (Div. 2) 8
228 The Child and Binary Tree Categories Codeforces Codeforces Round #250 (Div. 1) 8
229 Fractions Categories UVA 8
230 REQ Categories Codeforces Codeforces Round #330 (Div. 1) 8
231 Cows and Cool Sequences Categories Codeforces Codeforces Round #174 (Div. 1) 8
232 Tractor College Categories Codeforces Codeforces Round #126 (Div. 2) 9
233 Rotatable Number Categories Codeforces Codeforces Round #183 (Div. 1) 9
234 Swap (Easy - Level 2) Categories SPOJ 9
235 White, Black and White Again Categories Codeforces Testing Round #6 9
236 Divisibility Rules Categories Codeforces Codeforces Round #116 (Div. 2, ACM-ICPC Rules) 9
237 Morrowindows Categories Codeforces Codeforces Beta Round #66 9
238 Visit of the Great Categories Codeforces Codeforces Round #118 (Div. 1) 9
239 Shaass and Painter Robot Categories Codeforces Codeforces Round #178 (Div. 2) 9
240 Superhero's Job Categories Codeforces VK Cup 2015 - Round 3 (unofficial online mirror, Div. 1 only) 9
241 Levko and Sets Categories Codeforces Codeforces Round #210 (Div. 1) 9
242 Present for Vitalik the Philatelist Categories Codeforces Codeforces Round #325 (Div. 1) 9
243 Four Divisors Categories Codeforces Educational Codeforces Round 12 9
244 Jzzhu and Squares Categories Codeforces Codeforces Round #257 (Div. 1) 10
245 Nephren Runs a Cinema Categories Codeforces Codeforces Round #449 (Div. 1) 10
246 Number of Binominal Coefficients Categories Codeforces Codeforces Round #323 (Div. 1) 10
247 Mister B and Astronomers Categories Codeforces Codeforces Round #421 (Div. 1) 10
248 Prime factorization Categories Codeforces VK Cup 2012 Wild-card Round 1 10
249 Mister B and Beacons on Field Categories Codeforces Codeforces Round #421 (Div. 1) & Codeforces Round #421 (Div. 2) 10
250 New Year Running Categories Codeforces Good Bye 2014 10