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Problems Archives

The problems archives table shows problems 1 to 494. 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
440789
2Even Fibonacci numbers
362422
3Largest prime factor
263725
4Largest palindrome product
238687
5Smallest multiple
251582
6Sum square difference
253397
710001st prime
217160
8Largest product in a series
189615
9Special Pythagorean triplet
188582
10Summation of primes
173109
11Largest product in a grid
128926
12Highly divisible triangular number
117537
13Large sum
124148
14Longest Collatz sequence
122121
15Lattice paths
101782
16Power digit sum
126817
17Number letter counts
83792
18Maximum path sum I
81588
19Counting Sundays
75480
20Factorial digit sum
114478
21Amicable numbers
81092
22Names scores
75649
23Non-abundant sums
57164
24Lexicographic permutations
65133
251000-digit Fibonacci number
88297
26Reciprocal cycles
46628
27Quadratic primes
49076
28Number spiral diagonals
64176
29Distinct powers
58929
30Digit fifth powers
62417
31Coin sums
46590
32Pandigital products
39855
33Digit cancelling fractions
40932
34Digit factorials
54232
35Circular primes
49462
36Double-base palindromes
52407
37Truncatable primes
42026
38Pandigital multiples
35738
39Integer right triangles
41450
40Champernowne's constant
46239
41Pandigital prime
38680
42Coded triangle numbers
43948
43Sub-string divisibility
33196
44Pentagon numbers
31961
45Triangular, pentagonal, and hexagonal
41713
46Goldbach's other conjecture
34074
47Distinct primes factors
32491
48Self powers
68878
49Prime permutations
32316
50Consecutive prime sum
34676