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Problems Archives

The problems archives table shows problems 1 to 617. 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
753021
2Even Fibonacci numbers
605092
3Largest prime factor
433309
4Largest palindrome product
385686
5Smallest multiple
394076
6Sum square difference
396421
710001st prime
339344
8Largest product in a series
286640
9Special Pythagorean triplet
289518
10Summation of primes
265603
11Largest product in a grid
192582
12Highly divisible triangular number
179983
13Large sum
185633
14Longest Collatz sequence
185114
15Lattice paths
153162
16Power digit sum
187340
17Number letter counts
124590
18Maximum path sum I
119805
19Counting Sundays
111286
20Factorial digit sum
164189
21Amicable numbers
120085
22Names scores
110925
23Non-abundant sums
85234
24Lexicographic permutations
94787
251000-digit Fibonacci number
128209
26Reciprocal cycles
68758
27Quadratic primes
71848
28Number spiral diagonals
90411
29Distinct powers
86354
30Digit fifth powers
90490
31Coin sums
69230
32Pandigital products
58381
33Digit cancelling fractions
59096
34Digit factorials
77791
35Circular primes
70162
36Double-base palindromes
73917
37Truncatable primes
60670
38Pandigital multiples
51698
39Integer right triangles
60144
40Champernowne's constant
66260
41Pandigital prime
55980
42Coded triangle numbers
61875
43Sub-string divisibility
48820
44Pentagon numbers
47416
45Triangular, pentagonal, and hexagonal
58854
46Goldbach's other conjecture
50185
47Distinct primes factors
47424
48Self powers
94424
49Prime permutations
47394
50Consecutive prime sum
51039