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Problems Archives

The problems archives table shows problems 1 to 713. 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
958654
2Even Fibonacci numbers
762765
3Largest prime factor
546094
4Largest palindrome product
482200
5Smallest multiple
486019
6Sum square difference
489000
710001st prime
417659
8Largest product in a series
348631
9Special Pythagorean triplet
354149
10Summation of primes
323938
11Largest product in a grid
231219
12Highly divisible triangular number
217989
13Large sum
223213
14Longest Collatz sequence
223531
15Lattice paths
184004
16Power digit sum
225907
17Number letter counts
148706
18Maximum path sum I
142305
19Counting Sundays
132258
20Factorial digit sum
195358
21Amicable numbers
143609
22Names scores
131657
23Non-abundant sums
101695
24Lexicographic permutations
112267
251000-digit Fibonacci number
152661
26Reciprocal cycles
81769
27Quadratic primes
85125
28Number spiral diagonals
105876
29Distinct powers
103046
30Digit fifth powers
107720
31Coin sums
82927
32Pandigital products
69237
33Digit cancelling fractions
69741
34Digit factorials
92127
35Circular primes
82551
36Double-base palindromes
86703
37Truncatable primes
71548
38Pandigital multiples
61110
39Integer right triangles
71135
40Champernowne's constant
77995
41Pandigital prime
66098
42Coded triangle numbers
72381
43Sub-string divisibility
57888
44Pentagon numbers
56572
45Triangular, pentagonal, and hexagonal
69079
46Goldbach's other conjecture
59639
47Distinct primes factors
56098
48Self powers
109992
49Prime permutations
56003
50Consecutive prime sum
60555