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Problems Archives

The problems archives table shows problems 1 to 536. 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
537386
2Even Fibonacci numbers
438476
3Largest prime factor
317296
4Largest palindrome product
285482
5Smallest multiple
297157
6Sum square difference
298870
710001st prime
256075
8Largest product in a series
220410
9Special Pythagorean triplet
220744
10Summation of primes
202754
11Largest product in a grid
149460
12Highly divisible triangular number
137643
13Large sum
143892
14Longest Collatz sequence
142277
15Lattice paths
118274
16Power digit sum
145953
17Number letter counts
97042
18Maximum path sum I
94090
19Counting Sundays
87130
20Factorial digit sum
130463
21Amicable numbers
93710
22Names scores
86951
23Non-abundant sums
66195
24Lexicographic permutations
74745
251000-digit Fibonacci number
101032
26Reciprocal cycles
53796
27Quadratic primes
56469
28Number spiral diagonals
72620
29Distinct powers
67691
30Digit fifth powers
71367
31Coin sums
53872
32Pandigital products
45920
33Digit cancelling fractions
46839
34Digit factorials
61829
35Circular primes
56161
36Double-base palindromes
59401
37Truncatable primes
48161
38Pandigital multiples
40978
39Integer right triangles
47484
40Champernowne's constant
52660
41Pandigital prime
44288
42Coded triangle numbers
49678
43Sub-string divisibility
38233
44Pentagon numbers
36961
45Triangular, pentagonal, and hexagonal
47190
46Goldbach's other conjecture
39233
47Distinct primes factors
37312
48Self powers
76914
49Prime permutations
37233
50Consecutive prime sum
39930