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Problems Archives

The problems archives table shows problems 1 to 679. 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
896847
2Even Fibonacci numbers
714906
3Largest prime factor
510895
4Largest palindrome product
451871
5Smallest multiple
457161
6Sum square difference
460190
710001st prime
393111
8Largest product in a series
328723
9Special Pythagorean triplet
333697
10Summation of primes
305308
11Largest product in a grid
218697
12Highly divisible triangular number
205483
13Large sum
210992
14Longest Collatz sequence
211035
15Lattice paths
173945
16Power digit sum
213371
17Number letter counts
140718
18Maximum path sum I
134804
19Counting Sundays
125398
20Factorial digit sum
185196
21Amicable numbers
135869
22Names scores
124820
23Non-abundant sums
96235
24Lexicographic permutations
106498
251000-digit Fibonacci number
144841
26Reciprocal cycles
77475
27Quadratic primes
80728
28Number spiral diagonals
100794
29Distinct powers
97574
30Digit fifth powers
102048
31Coin sums
78359
32Pandigital products
65545
33Digit cancelling fractions
66109
34Digit factorials
87324
35Circular primes
78403
36Double-base palindromes
82511
37Truncatable primes
67915
38Pandigital multiples
57933
39Integer right triangles
67424
40Champernowne's constant
74147
41Pandigital prime
62730
42Coded triangle numbers
68864
43Sub-string divisibility
54841
44Pentagon numbers
53551
45Triangular, pentagonal, and hexagonal
65730
46Goldbach's other conjecture
56520
47Distinct primes factors
53244
48Self powers
105051
49Prime permutations
53204
50Consecutive prime sum
57420