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Problems Archives

The problems archives table shows problems 1 to 667. 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
873404
2Even Fibonacci numbers
697323
3Largest prime factor
498431
4Largest palindrome product
441218
5Smallest multiple
446972
6Sum square difference
449942
710001st prime
384476
8Largest product in a series
321871
9Special Pythagorean triplet
326696
10Summation of primes
298955
11Largest product in a grid
214539
12Highly divisible triangular number
201436
13Large sum
206948
14Longest Collatz sequence
206857
15Lattice paths
170583
16Power digit sum
209113
17Number letter counts
138145
18Maximum path sum I
132389
19Counting Sundays
123086
20Factorial digit sum
181813
21Amicable numbers
133288
22Names scores
122548
23Non-abundant sums
94425
24Lexicographic permutations
104605
251000-digit Fibonacci number
142109
26Reciprocal cycles
76087
27Quadratic primes
79283
28Number spiral diagonals
99147
29Distinct powers
95662
30Digit fifth powers
100168
31Coin sums
76910
32Pandigital products
64414
33Digit cancelling fractions
65024
34Digit factorials
85821
35Circular primes
77073
36Double-base palindromes
81097
37Truncatable primes
66764
38Pandigital multiples
56971
39Integer right triangles
66292
40Champernowne's constant
72852
41Pandigital prime
61650
42Coded triangle numbers
67757
43Sub-string divisibility
53903
44Pentagon numbers
52564
45Triangular, pentagonal, and hexagonal
64658
46Goldbach's other conjecture
55499
47Distinct primes factors
52302
48Self powers
103263
49Prime permutations
52257
50Consecutive prime sum
56397