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Problems Archives

The problems archives table shows problems 1 to 512. 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
488294
2Even Fibonacci numbers
400233
3Largest prime factor
290565
4Largest palindrome product
262389
5Smallest multiple
274421
6Sum square difference
276309
710001st prime
236872
8Largest product in a series
205311
9Special Pythagorean triplet
204938
10Summation of primes
188171
11Largest product in a grid
139458
12Highly divisible triangular number
127816
13Large sum
134233
14Longest Collatz sequence
132380
15Lattice paths
110246
16Power digit sum
136570
17Number letter counts
90628
18Maximum path sum I
88149
19Counting Sundays
81441
20Factorial digit sum
122643
21Amicable numbers
87558
22Names scores
81496
23Non-abundant sums
61859
24Lexicographic permutations
70090
251000-digit Fibonacci number
94756
26Reciprocal cycles
50378
27Quadratic primes
52985
28Number spiral diagonals
68529
29Distinct powers
63466
30Digit fifth powers
67070
31Coin sums
50412
32Pandigital products
43056
33Digit cancelling fractions
44072
34Digit factorials
58155
35Circular primes
52981
36Double-base palindromes
56067
37Truncatable primes
45261
38Pandigital multiples
38511
39Integer right triangles
44598
40Champernowne's constant
49517
41Pandigital prime
41607
42Coded triangle numbers
46963
43Sub-string divisibility
35841
44Pentagon numbers
34598
45Triangular, pentagonal, and hexagonal
44588
46Goldbach's other conjecture
36778
47Distinct primes factors
35023
48Self powers
73037
49Prime permutations
34905
50Consecutive prime sum
37449