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Problems Archives

The problems archives table shows problems 1 to 670. 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
882224
2Even Fibonacci numbers
703886
3Largest prime factor
503058
4Largest palindrome product
445178
5Smallest multiple
450700
6Sum square difference
453702
710001st prime
387687
8Largest product in a series
324402
9Special Pythagorean triplet
329341
10Summation of primes
301319
11Largest product in a grid
216088
12Highly divisible triangular number
202927
13Large sum
208403
14Longest Collatz sequence
208388
15Lattice paths
171794
16Power digit sum
210651
17Number letter counts
139086
18Maximum path sum I
133259
19Counting Sundays
123928
20Factorial digit sum
183064
21Amicable numbers
134230
22Names scores
123331
23Non-abundant sums
95074
24Lexicographic permutations
105297
251000-digit Fibonacci number
143094
26Reciprocal cycles
76593
27Quadratic primes
79776
28Number spiral diagonals
99747
29Distinct powers
96364
30Digit fifth powers
100839
31Coin sums
77445
32Pandigital products
64832
33Digit cancelling fractions
65414
34Digit factorials
86355
35Circular primes
77575
36Double-base palindromes
81620
37Truncatable primes
67200
38Pandigital multiples
57336
39Integer right triangles
66698
40Champernowne's constant
73307
41Pandigital prime
62049
42Coded triangle numbers
68174
43Sub-string divisibility
54249
44Pentagon numbers
52899
45Triangular, pentagonal, and hexagonal
65026
46Goldbach's other conjecture
55871
47Distinct primes factors
52658
48Self powers
103922
49Prime permutations
52627
50Consecutive prime sum
56748