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Problems Archives

The problems archives table shows problems 1 to 495. 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
441789
2Even Fibonacci numbers
363191
3Largest prime factor
264292
4Largest palindrome product
239219
5Smallest multiple
252095
6Sum square difference
253901
710001st prime
217577
8Largest product in a series
189948
9Special Pythagorean triplet
188932
10Summation of primes
173424
11Largest product in a grid
129148
12Highly divisible triangular number
117761
13Large sum
124351
14Longest Collatz sequence
122315
15Lattice paths
101951
16Power digit sum
127000
17Number letter counts
83928
18Maximum path sum I
81713
19Counting Sundays
75610
20Factorial digit sum
114663
21Amicable numbers
81217
22Names scores
75770
23Non-abundant sums
57253
24Lexicographic permutations
65233
251000-digit Fibonacci number
88429
26Reciprocal cycles
46705
27Quadratic primes
49156
28Number spiral diagonals
64261
29Distinct powers
59021
30Digit fifth powers
62508
31Coin sums
46660
32Pandigital products
39907
33Digit cancelling fractions
40997
34Digit factorials
54322
35Circular primes
49548
36Double-base palindromes
52486
37Truncatable primes
42088
38Pandigital multiples
35789
39Integer right triangles
41514
40Champernowne's constant
46290
41Pandigital prime
38744
42Coded triangle numbers
44004
43Sub-string divisibility
33237
44Pentagon numbers
32004
45Triangular, pentagonal, and hexagonal
41774
46Goldbach's other conjecture
34127
47Distinct primes factors
32535
48Self powers
68971
49Prime permutations
32367
50Consecutive prime sum
34734