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Problems Archives

The problems archives table shows problems 1 to 502. 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
454676
2Even Fibonacci numbers
373449
3Largest prime factor
271647
4Largest palindrome product
245700
5Smallest multiple
258359
6Sum square difference
260210
710001st prime
223084
8Largest product in a series
194260
9Special Pythagorean triplet
193461
10Summation of primes
177628
11Largest product in a grid
132019
12Highly divisible triangular number
120608
13Large sum
127163
14Longest Collatz sequence
125147
15Lattice paths
104324
16Power digit sum
129689
17Number letter counts
85790
18Maximum path sum I
83569
19Counting Sundays
77295
20Factorial digit sum
116915
21Amicable numbers
83030
22Names scores
77399
23Non-abundant sums
58570
24Lexicographic permutations
66613
251000-digit Fibonacci number
90259
26Reciprocal cycles
47765
27Quadratic primes
50256
28Number spiral diagonals
65525
29Distinct powers
60300
30Digit fifth powers
63782
31Coin sums
47731
32Pandigital products
40809
33Digit cancelling fractions
41888
34Digit factorials
55437
35Circular primes
50512
36Double-base palindromes
53493
37Truncatable primes
42989
38Pandigital multiples
36551
39Integer right triangles
42383
40Champernowne's constant
47199
41Pandigital prime
39557
42Coded triangle numbers
44846
43Sub-string divisibility
33975
44Pentagon numbers
32749
45Triangular, pentagonal, and hexagonal
42549
46Goldbach's other conjecture
34915
47Distinct primes factors
33224
48Self powers
70159
49Prime permutations
33082
50Consecutive prime sum
35492