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Problems Archives

The problems archives table shows problems 1 to 707. 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
948815
2Even Fibonacci numbers
755131
3Largest prime factor
540459
4Largest palindrome product
477271
5Smallest multiple
481387
6Sum square difference
484317
710001st prime
413655
8Largest product in a series
345340
9Special Pythagorean triplet
350843
10Summation of primes
320860
11Largest product in a grid
229109
12Highly divisible triangular number
215798
13Large sum
221113
14Longest Collatz sequence
221451
15Lattice paths
182292
16Power digit sum
223742
17Number letter counts
147315
18Maximum path sum I
141052
19Counting Sundays
131090
20Factorial digit sum
193601
21Amicable numbers
142258
22Names scores
130443
23Non-abundant sums
100744
24Lexicographic permutations
111240
251000-digit Fibonacci number
151338
26Reciprocal cycles
81008
27Quadratic primes
84321
28Number spiral diagonals
105020
29Distinct powers
102113
30Digit fifth powers
106741
31Coin sums
82108
32Pandigital products
68544
33Digit cancelling fractions
69073
34Digit factorials
91259
35Circular primes
81811
36Double-base palindromes
85963
37Truncatable primes
70891
38Pandigital multiples
60502
39Integer right triangles
70456
40Champernowne's constant
77277
41Pandigital prime
65439
42Coded triangle numbers
71730
43Sub-string divisibility
57293
44Pentagon numbers
55994
45Triangular, pentagonal, and hexagonal
68443
46Goldbach's other conjecture
59066
47Distinct primes factors
55541
48Self powers
109105
49Prime permutations
55470
50Consecutive prime sum
59966