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Problems Archives

The problems archives table shows problems 1 to 598. 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
685293
2Even Fibonacci numbers
553523
3Largest prime factor
397554
4Largest palindrome product
355229
5Smallest multiple
364618
6Sum square difference
366653
710001st prime
314207
8Largest product in a series
266892
9Special Pythagorean triplet
268879
10Summation of primes
246891
11Largest product in a grid
180080
12Highly divisible triangular number
167663
13Large sum
173392
14Longest Collatz sequence
172602
15Lattice paths
142926
16Power digit sum
175024
17Number letter counts
116718
18Maximum path sum I
112436
19Counting Sundays
104416
20Factorial digit sum
154317
21Amicable numbers
112406
22Names scores
103946
23Non-abundant sums
79831
24Lexicographic permutations
88988
251000-digit Fibonacci number
120279
26Reciprocal cycles
64488
27Quadratic primes
67483
28Number spiral diagonals
85303
29Distinct powers
81007
30Digit fifth powers
84907
31Coin sums
64761
32Pandigital products
54842
33Digit cancelling fractions
55565
34Digit factorials
73199
35Circular primes
66154
36Double-base palindromes
69584
37Truncatable primes
57066
38Pandigital multiples
48639
39Integer right triangles
56440
40Champernowne's constant
62351
41Pandigital prime
52592
42Coded triangle numbers
58350
43Sub-string divisibility
45772
44Pentagon numbers
44425
45Triangular, pentagonal, and hexagonal
55482
46Goldbach's other conjecture
47017
47Distinct primes factors
44524
48Self powers
89133
49Prime permutations
44478
50Consecutive prime sum
47823