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Problems Archives

The problems archives table shows problems 1 to 626. 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
780940
2Even Fibonacci numbers
626411
3Largest prime factor
448282
4Largest palindrome product
398631
5Smallest multiple
406428
6Sum square difference
408769
710001st prime
349898
8Largest product in a series
294929
9Special Pythagorean triplet
298143
10Summation of primes
273340
11Largest product in a grid
197745
12Highly divisible triangular number
185064
13Large sum
190642
14Longest Collatz sequence
190332
15Lattice paths
157224
16Power digit sum
192393
17Number letter counts
127885
18Maximum path sum I
122823
19Counting Sundays
114150
20Factorial digit sum
168359
21Amicable numbers
123323
22Names scores
113792
23Non-abundant sums
87509
24Lexicographic permutations
97176
251000-digit Fibonacci number
131503
26Reciprocal cycles
70520
27Quadratic primes
73668
28Number spiral diagonals
92468
29Distinct powers
88608
30Digit fifth powers
92814
31Coin sums
71064
32Pandigital products
59852
33Digit cancelling fractions
60571
34Digit factorials
79687
35Circular primes
71895
36Double-base palindromes
75702
37Truncatable primes
62225
38Pandigital multiples
52994
39Integer right triangles
61672
40Champernowne's constant
67882
41Pandigital prime
57390
42Coded triangle numbers
63310
43Sub-string divisibility
50125
44Pentagon numbers
48684
45Triangular, pentagonal, and hexagonal
60318
46Goldbach's other conjecture
51510
47Distinct primes factors
48630
48Self powers
96519
49Prime permutations
48624
50Consecutive prime sum
52349