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Problems Archives

The problems archives table shows problems 1 to 615. 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
746098
2Even Fibonacci numbers
599767
3Largest prime factor
429611
4Largest palindrome product
382599
5Smallest multiple
391103
6Sum square difference
393341
710001st prime
336715
8Largest product in a series
284591
9Special Pythagorean triplet
287356
10Summation of primes
263582
11Largest product in a grid
191218
12Highly divisible triangular number
178510
13Large sum
184306
14Longest Collatz sequence
183805
15Lattice paths
151933
16Power digit sum
185966
17Number letter counts
123741
18Maximum path sum I
118935
19Counting Sundays
110543
20Factorial digit sum
163088
21Amicable numbers
119165
22Names scores
110163
23Non-abundant sums
84616
24Lexicographic permutations
94088
251000-digit Fibonacci number
127337
26Reciprocal cycles
68253
27Quadratic primes
71386
28Number spiral diagonals
89851
29Distinct powers
85741
30Digit fifth powers
89866
31Coin sums
68660
32Pandigital products
57980
33Digit cancelling fractions
58635
34Digit factorials
77224
35Circular primes
69685
36Double-base palindromes
73418
37Truncatable primes
60217
38Pandigital multiples
51313
39Integer right triangles
59662
40Champernowne's constant
65805
41Pandigital prime
55566
42Coded triangle numbers
61454
43Sub-string divisibility
48470
44Pentagon numbers
47048
45Triangular, pentagonal, and hexagonal
58432
46Goldbach's other conjecture
49799
47Distinct primes factors
47064
48Self powers
93733
49Prime permutations
47050
50Consecutive prime sum
50663