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Problems Archives

The problems archives table shows problems 1 to 627. 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
783522
2Even Fibonacci numbers
628322
3Largest prime factor
449571
4Largest palindrome product
399744
5Smallest multiple
407504
6Sum square difference
409887
710001st prime
350775
8Largest product in a series
295619
9Special Pythagorean triplet
298823
10Summation of primes
273957
11Largest product in a grid
198113
12Highly divisible triangular number
185476
13Large sum
191015
14Longest Collatz sequence
190744
15Lattice paths
157510
16Power digit sum
192781
17Number letter counts
128111
18Maximum path sum I
123052
19Counting Sundays
114336
20Factorial digit sum
168670
21Amicable numbers
123559
22Names scores
113981
23Non-abundant sums
87671
24Lexicographic permutations
97348
251000-digit Fibonacci number
131767
26Reciprocal cycles
70641
27Quadratic primes
73789
28Number spiral diagonals
92598
29Distinct powers
88765
30Digit fifth powers
92965
31Coin sums
71176
32Pandigital products
59928
33Digit cancelling fractions
60644
34Digit factorials
79791
35Circular primes
72000
36Double-base palindromes
75808
37Truncatable primes
62318
38Pandigital multiples
53085
39Integer right triangles
61779
40Champernowne's constant
67988
41Pandigital prime
57495
42Coded triangle numbers
63417
43Sub-string divisibility
50219
44Pentagon numbers
48758
45Triangular, pentagonal, and hexagonal
60416
46Goldbach's other conjecture
51594
47Distinct primes factors
48712
48Self powers
96679
49Prime permutations
48718
50Consecutive prime sum
52443