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