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Problems Archives

The problems archives table shows problems 1 to 536. 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
537317
2Even Fibonacci numbers
438423
3Largest prime factor
317261
4Largest palindrome product
285452
5Smallest multiple
297126
6Sum square difference
298850
710001st prime
256056
8Largest product in a series
220393
9Special Pythagorean triplet
220721
10Summation of primes
202739
11Largest product in a grid
149445
12Highly divisible triangular number
137624
13Large sum
143878
14Longest Collatz sequence
142262
15Lattice paths
118266
16Power digit sum
145939
17Number letter counts
97032
18Maximum path sum I
94086
19Counting Sundays
87119
20Factorial digit sum
130454
21Amicable numbers
93703
22Names scores
86944
23Non-abundant sums
66188
24Lexicographic permutations
74739
251000-digit Fibonacci number
101024
26Reciprocal cycles
53792
27Quadratic primes
56465
28Number spiral diagonals
72618
29Distinct powers
67687
30Digit fifth powers
71365
31Coin sums
53868
32Pandigital products
45918
33Digit cancelling fractions
46837
34Digit factorials
61821
35Circular primes
56158
36Double-base palindromes
59397
37Truncatable primes
48159
38Pandigital multiples
40975
39Integer right triangles
47479
40Champernowne's constant
52653
41Pandigital prime
44282
42Coded triangle numbers
49676
43Sub-string divisibility
38226
44Pentagon numbers
36959
45Triangular, pentagonal, and hexagonal
47188
46Goldbach's other conjecture
39229
47Distinct primes factors
37312
48Self powers
76905
49Prime permutations
37233
50Consecutive prime sum
39927