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Problems Archives

The problems archives table shows problems 1 to 646. 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
826856
2Even Fibonacci numbers
661247
3Largest prime factor
472404
4Largest palindrome product
418771
5Smallest multiple
425808
6Sum square difference
428437
710001st prime
366250
8Largest product in a series
307550
9Special Pythagorean triplet
311606
10Summation of primes
285298
11Largest product in a grid
205704
12Highly divisible triangular number
192793
13Large sum
198263
14Longest Collatz sequence
198118
15Lattice paths
163596
16Power digit sum
200204
17Number letter counts
132675
18Maximum path sum I
127240
19Counting Sundays
118433
20Factorial digit sum
174527
21Amicable numbers
127952
22Names scores
117878
23Non-abundant sums
90767
24Lexicographic permutations
100703
251000-digit Fibonacci number
136511
26Reciprocal cycles
73197
27Quadratic primes
76290
28Number spiral diagonals
95710
29Distinct powers
91857
30Digit fifth powers
96213
31Coin sums
73890
32Pandigital products
61963
33Digit cancelling fractions
62615
34Digit factorials
82558
35Circular primes
74263
36Double-base palindromes
78233
37Truncatable primes
64281
38Pandigital multiples
54817
39Integer right triangles
63816
40Champernowne's constant
70178
41Pandigital prime
59398
42Coded triangle numbers
65333
43Sub-string divisibility
51861
44Pentagon numbers
50476
45Triangular, pentagonal, and hexagonal
62342
46Goldbach's other conjecture
53320
47Distinct primes factors
50291
48Self powers
99658
49Prime permutations
50323
50Consecutive prime sum
54204