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Problems Archives

The problems archives table shows problems 1 to 507. 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
462830
2Even Fibonacci numbers
379917
3Largest prime factor
276234
4Largest palindrome product
249773
5Smallest multiple
262299
6Sum square difference
264116
710001st prime
226382
8Largest product in a series
196934
9Special Pythagorean triplet
196261
10Summation of primes
180167
11Largest product in a grid
133816
12Highly divisible triangular number
122378
13Large sum
128905
14Longest Collatz sequence
126938
15Lattice paths
105834
16Power digit sum
131412
17Number letter counts
86998
18Maximum path sum I
84708
19Counting Sundays
78316
20Factorial digit sum
118335
21Amicable numbers
84146
22Names scores
78418
23Non-abundant sums
59373
24Lexicographic permutations
67435
251000-digit Fibonacci number
91332
26Reciprocal cycles
48401
27Quadratic primes
50907
28Number spiral diagonals
66242
29Distinct powers
61055
30Digit fifth powers
64574
31Coin sums
48384
32Pandigital products
41347
33Digit cancelling fractions
42392
34Digit factorials
56073
35Circular primes
51075
36Double-base palindromes
54070
37Truncatable primes
43525
38Pandigital multiples
36975
39Integer right triangles
42893
40Champernowne's constant
47744
41Pandigital prime
40041
42Coded triangle numbers
45356
43Sub-string divisibility
34422
44Pentagon numbers
33196
45Triangular, pentagonal, and hexagonal
43039
46Goldbach's other conjecture
35352
47Distinct primes factors
33666
48Self powers
70883
49Prime permutations
33528
50Consecutive prime sum
35986