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Problems Archives

The problems archives table shows problems 1 to 692. 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
920197
2Even Fibonacci numbers
732845
3Largest prime factor
523766
4Largest palindrome product
462905
5Smallest multiple
467776
6Sum square difference
470833
710001st prime
401931
8Largest product in a series
335869
9Special Pythagorean triplet
341122
10Summation of primes
311997
11Largest product in a grid
223166
12Highly divisible triangular number
209888
13Large sum
215426
14Longest Collatz sequence
215616
15Lattice paths
177548
16Power digit sum
217839
17Number letter counts
143564
18Maximum path sum I
137497
19Counting Sundays
127882
20Factorial digit sum
188848
21Amicable numbers
138644
22Names scores
127254
23Non-abundant sums
98143
24Lexicographic permutations
108522
251000-digit Fibonacci number
147716
26Reciprocal cycles
79030
27Quadratic primes
82302
28Number spiral diagonals
102736
29Distinct powers
99590
30Digit fifth powers
104172
31Coin sums
80037
32Pandigital products
66869
33Digit cancelling fractions
67441
34Digit factorials
89092
35Circular primes
79960
36Double-base palindromes
84018
37Truncatable primes
69243
38Pandigital multiples
59121
39Integer right triangles
68807
40Champernowne's constant
75557
41Pandigital prime
63915
42Coded triangle numbers
70140
43Sub-string divisibility
55917
44Pentagon numbers
54644
45Triangular, pentagonal, and hexagonal
66968
46Goldbach's other conjecture
57643
47Distinct primes factors
54288
48Self powers
106887
49Prime permutations
54203
50Consecutive prime sum
58544