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Problems Archives

The problems archives table shows problems 1 to 665. 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
856916
2Even Fibonacci numbers
684460
3Largest prime factor
489002
4Largest palindrome product
433197
5Smallest multiple
439348
6Sum square difference
442162
710001st prime
377939
8Largest product in a series
316550
9Special Pythagorean triplet
321209
10Summation of primes
294070
11Largest product in a grid
211344
12Highly divisible triangular number
198290
13Large sum
203777
14Longest Collatz sequence
203622
15Lattice paths
168066
16Power digit sum
205808
17Number letter counts
136143
18Maximum path sum I
130555
19Counting Sundays
121383
20Factorial digit sum
179117
21Amicable numbers
131334
22Names scores
120891
23Non-abundant sums
93073
24Lexicographic permutations
103142
251000-digit Fibonacci number
140056
26Reciprocal cycles
75018
27Quadratic primes
78157
28Number spiral diagonals
97873
29Distinct powers
94253
30Digit fifth powers
98746
31Coin sums
75815
32Pandigital products
63499
33Digit cancelling fractions
64113
34Digit factorials
84597
35Circular primes
76020
36Double-base palindromes
80048
37Truncatable primes
65825
38Pandigital multiples
56143
39Integer right triangles
65331
40Champernowne's constant
71841
41Pandigital prime
60791
42Coded triangle numbers
66861
43Sub-string divisibility
53112
44Pentagon numbers
51787
45Triangular, pentagonal, and hexagonal
63794
46Goldbach's other conjecture
54682
47Distinct primes factors
51553
48Self powers
101989
49Prime permutations
51527
50Consecutive prime sum
55586