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Problems Archives

The problems archives table shows problems 1 to 507. 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
464264
2Even Fibonacci numbers
381074
3Largest prime factor
277051
4Largest palindrome product
250455
5Smallest multiple
262988
6Sum square difference
264815
710001st prime
226993
8Largest product in a series
197406
9Special Pythagorean triplet
196760
10Summation of primes
180648
11Largest product in a grid
134150
12Highly divisible triangular number
122685
13Large sum
129205
14Longest Collatz sequence
127267
15Lattice paths
106104
16Power digit sum
131720
17Number letter counts
87202
18Maximum path sum I
84907
19Counting Sundays
78488
20Factorial digit sum
118579
21Amicable numbers
84340
22Names scores
78597
23Non-abundant sums
59516
24Lexicographic permutations
67584
251000-digit Fibonacci number
91535
26Reciprocal cycles
48538
27Quadratic primes
51021
28Number spiral diagonals
66386
29Distinct powers
61198
30Digit fifth powers
64726
31Coin sums
48489
32Pandigital products
41442
33Digit cancelling fractions
42498
34Digit factorials
56186
35Circular primes
51188
36Double-base palindromes
54193
37Truncatable primes
43634
38Pandigital multiples
37070
39Integer right triangles
42987
40Champernowne's constant
47830
41Pandigital prime
40128
42Coded triangle numbers
45450
43Sub-string divisibility
34492
44Pentagon numbers
33273
45Triangular, pentagonal, and hexagonal
43118
46Goldbach's other conjecture
35411
47Distinct primes factors
33751
48Self powers
70999
49Prime permutations
33600
50Consecutive prime sum
36067