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Problems Archives

The problems archives table shows problems 1 to 495. If you would like to tackle the 10 most recently published problems then go to Recent problems.
Click the description/title of the problem to view details and submit your answer.


IDDescription / TitleSolved By
1Multiples of 3 and 5
441969
2Even Fibonacci numbers
363334
3Largest prime factor
264396
4Largest palindrome product
239309
5Smallest multiple
252178
6Sum square difference
253995
710001st prime
217660
8Largest product in a series
189995
9Special Pythagorean triplet
188984
10Summation of primes
173470
11Largest product in a grid
129180
12Highly divisible triangular number
117800
13Large sum
124385
14Longest Collatz sequence
122349
15Lattice paths
101982
16Power digit sum
127037
17Number letter counts
83953
18Maximum path sum I
81745
19Counting Sundays
75625
20Factorial digit sum
114689
21Amicable numbers
81235
22Names scores
75792
23Non-abundant sums
57272
24Lexicographic permutations
65256
251000-digit Fibonacci number
88457
26Reciprocal cycles
46721
27Quadratic primes
49169
28Number spiral diagonals
64279
29Distinct powers
59039
30Digit fifth powers
62527
31Coin sums
46675
32Pandigital products
39925
33Digit cancelling fractions
41012
34Digit factorials
54333
35Circular primes
49560
36Double-base palindromes
52500
37Truncatable primes
42099
38Pandigital multiples
35800
39Integer right triangles
41523
40Champernowne's constant
46309
41Pandigital prime
38751
42Coded triangle numbers
44013
43Sub-string divisibility
33249
44Pentagon numbers
32012
45Triangular, pentagonal, and hexagonal
41780
46Goldbach's other conjecture
34139
47Distinct primes factors
32541
48Self powers
68985
49Prime permutations
32372
50Consecutive prime sum
34741