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Problems Archives

The problems archives table shows problems 1 to 642. 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
817111
2Even Fibonacci numbers
653786
3Largest prime factor
467269
4Largest palindrome product
414443
5Smallest multiple
421752
6Sum square difference
424351
710001st prime
362844
8Largest product in a series
304987
9Special Pythagorean triplet
308874
10Summation of primes
282786
11Largest product in a grid
204051
12Highly divisible triangular number
191251
13Large sum
196668
14Longest Collatz sequence
196520
15Lattice paths
162364
16Power digit sum
198597
17Number letter counts
131676
18Maximum path sum I
126371
19Counting Sundays
117573
20Factorial digit sum
173263
21Amicable numbers
127028
22Names scores
117064
23Non-abundant sums
90107
24Lexicographic permutations
100009
251000-digit Fibonacci number
135507
26Reciprocal cycles
72669
27Quadratic primes
75772
28Number spiral diagonals
95116
29Distinct powers
91214
30Digit fifth powers
95567
31Coin sums
73410
32Pandigital products
61550
33Digit cancelling fractions
62207
34Digit factorials
81993
35Circular primes
73804
36Double-base palindromes
77709
37Truncatable primes
63861
38Pandigital multiples
54443
39Integer right triangles
63400
40Champernowne's constant
69703
41Pandigital prime
59021
42Coded triangle numbers
64936
43Sub-string divisibility
51520
44Pentagon numbers
50099
45Triangular, pentagonal, and hexagonal
61921
46Goldbach's other conjecture
52947
47Distinct primes factors
49948
48Self powers
99067
49Prime permutations
49998
50Consecutive prime sum
53853