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Problems Archives

The problems archives table shows problems 1 to 667. 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
872904
2Even Fibonacci numbers
696949
3Largest prime factor
498132
4Largest palindrome product
440973
5Smallest multiple
446754
6Sum square difference
449705
710001st prime
384287
8Largest product in a series
321696
9Special Pythagorean triplet
326539
10Summation of primes
298799
11Largest product in a grid
214435
12Highly divisible triangular number
201345
13Large sum
206846
14Longest Collatz sequence
206759
15Lattice paths
170483
16Power digit sum
209012
17Number letter counts
138073
18Maximum path sum I
132312
19Counting Sundays
123023
20Factorial digit sum
181717
21Amicable numbers
133225
22Names scores
122484
23Non-abundant sums
94370
24Lexicographic permutations
104543
251000-digit Fibonacci number
142037
26Reciprocal cycles
76056
27Quadratic primes
79257
28Number spiral diagonals
99116
29Distinct powers
95619
30Digit fifth powers
100116
31Coin sums
76874
32Pandigital products
64389
33Digit cancelling fractions
64995
34Digit factorials
85787
35Circular primes
77039
36Double-base palindromes
81067
37Truncatable primes
66730
38Pandigital multiples
56943
39Integer right triangles
66264
40Champernowne's constant
72824
41Pandigital prime
61624
42Coded triangle numbers
67729
43Sub-string divisibility
53876
44Pentagon numbers
52543
45Triangular, pentagonal, and hexagonal
64637
46Goldbach's other conjecture
55482
47Distinct primes factors
52281
48Self powers
103240
49Prime permutations
52239
50Consecutive prime sum
56371