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Problems Archives

The problems archives table shows problems 1 to 619. 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
759501
2Even Fibonacci numbers
610069
3Largest prime factor
436831
4Largest palindrome product
388746
5Smallest multiple
396937
6Sum square difference
399307
710001st prime
341820
8Largest product in a series
288609
9Special Pythagorean triplet
291575
10Summation of primes
267404
11Largest product in a grid
193784
12Highly divisible triangular number
181112
13Large sum
186787
14Longest Collatz sequence
186333
15Lattice paths
154081
16Power digit sum
188482
17Number letter counts
125331
18Maximum path sum I
120473
19Counting Sundays
111936
20Factorial digit sum
165144
21Amicable numbers
120841
22Names scores
111575
23Non-abundant sums
85743
24Lexicographic permutations
95299
251000-digit Fibonacci number
128968
26Reciprocal cycles
69149
27Quadratic primes
72264
28Number spiral diagonals
90863
29Distinct powers
86853
30Digit fifth powers
91015
31Coin sums
69659
32Pandigital products
58689
33Digit cancelling fractions
59399
34Digit factorials
78191
35Circular primes
70520
36Double-base palindromes
74312
37Truncatable primes
61005
38Pandigital multiples
51985
39Integer right triangles
60486
40Champernowne's constant
66621
41Pandigital prime
56300
42Coded triangle numbers
62194
43Sub-string divisibility
49098
44Pentagon numbers
47712
45Triangular, pentagonal, and hexagonal
59165
46Goldbach's other conjecture
50461
47Distinct primes factors
47683
48Self powers
94907
49Prime permutations
47667
50Consecutive prime sum
51325