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Problems Archives

The problems archives table shows problems 1 to 713. 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
958798
2Even Fibonacci numbers
762874
3Largest prime factor
546202
4Largest palindrome product
482276
5Smallest multiple
486084
6Sum square difference
489066
710001st prime
417713
8Largest product in a series
348667
9Special Pythagorean triplet
354194
10Summation of primes
323978
11Largest product in a grid
231251
12Highly divisible triangular number
218014
13Large sum
223242
14Longest Collatz sequence
223563
15Lattice paths
184027
16Power digit sum
225941
17Number letter counts
148734
18Maximum path sum I
142321
19Counting Sundays
132271
20Factorial digit sum
195374
21Amicable numbers
143628
22Names scores
131681
23Non-abundant sums
101709
24Lexicographic permutations
112282
251000-digit Fibonacci number
152683
26Reciprocal cycles
81781
27Quadratic primes
85133
28Number spiral diagonals
105885
29Distinct powers
103057
30Digit fifth powers
107734
31Coin sums
82936
32Pandigital products
69246
33Digit cancelling fractions
69747
34Digit factorials
92135
35Circular primes
82556
36Double-base palindromes
86716
37Truncatable primes
71557
38Pandigital multiples
61117
39Integer right triangles
71143
40Champernowne's constant
78004
41Pandigital prime
66113
42Coded triangle numbers
72391
43Sub-string divisibility
57897
44Pentagon numbers
56579
45Triangular, pentagonal, and hexagonal
69091
46Goldbach's other conjecture
59645
47Distinct primes factors
56103
48Self powers
109998
49Prime permutations
56009
50Consecutive prime sum
60561