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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
864152
2Even Fibonacci numbers
690102
3Largest prime factor
493250
4Largest palindrome product
436839
5Smallest multiple
442884
6Sum square difference
445754
710001st prime
380999
8Largest product in a series
319036
9Special Pythagorean triplet
323785
10Summation of primes
296339
11Largest product in a grid
212789
12Highly divisible triangular number
199700
13Large sum
205227
14Longest Collatz sequence
205066
15Lattice paths
169202
16Power digit sum
207324
17Number letter counts
137050
18Maximum path sum I
131386
19Counting Sundays
122145
20Factorial digit sum
180363
21Amicable numbers
132235
22Names scores
121658
23Non-abundant sums
93683
24Lexicographic permutations
103801
251000-digit Fibonacci number
140994
26Reciprocal cycles
75523
27Quadratic primes
78668
28Number spiral diagonals
98435
29Distinct powers
94902
30Digit fifth powers
99383
31Coin sums
76309
32Pandigital products
63918
33Digit cancelling fractions
64518
34Digit factorials
85138
35Circular primes
76478
36Double-base palindromes
80511
37Truncatable primes
66244
38Pandigital multiples
56516
39Integer right triangles
65753
40Champernowne's constant
72274
41Pandigital prime
61173
42Coded triangle numbers
67249
43Sub-string divisibility
53453
44Pentagon numbers
52131
45Triangular, pentagonal, and hexagonal
64169
46Goldbach's other conjecture
55040
47Distinct primes factors
51894
48Self powers
102558
49Prime permutations
51858
50Consecutive prime sum
55959