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Problems Archives

The problems archives table shows problems 1 to 506. 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
462678
2Even Fibonacci numbers
379796
3Largest prime factor
276152
4Largest palindrome product
249700
5Smallest multiple
262226
6Sum square difference
264046
710001st prime
226326
8Largest product in a series
196887
9Special Pythagorean triplet
196208
10Summation of primes
180121
11Largest product in a grid
133788
12Highly divisible triangular number
122342
13Large sum
128876
14Longest Collatz sequence
126914
15Lattice paths
105814
16Power digit sum
131386
17Number letter counts
86981
18Maximum path sum I
84688
19Counting Sundays
78296
20Factorial digit sum
118308
21Amicable numbers
84126
22Names scores
78396
23Non-abundant sums
59359
24Lexicographic permutations
67425
251000-digit Fibonacci number
91309
26Reciprocal cycles
48383
27Quadratic primes
50893
28Number spiral diagonals
66231
29Distinct powers
61040
30Digit fifth powers
64560
31Coin sums
48376
32Pandigital products
41335
33Digit cancelling fractions
42376
34Digit factorials
56058
35Circular primes
51062
36Double-base palindromes
54052
37Truncatable primes
43514
38Pandigital multiples
36967
39Integer right triangles
42886
40Champernowne's constant
47735
41Pandigital prime
40034
42Coded triangle numbers
45350
43Sub-string divisibility
34419
44Pentagon numbers
33183
45Triangular, pentagonal, and hexagonal
43029
46Goldbach's other conjecture
35345
47Distinct primes factors
33655
48Self powers
70870
49Prime permutations
33520
50Consecutive prime sum
35977