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Problems Archives

The problems archives table shows problems 1 to 495. 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
442601
2Even Fibonacci numbers
363846
3Largest prime factor
264763
4Largest palindrome product
239619
5Smallest multiple
252479
6Sum square difference
254288
710001st prime
217925
8Largest product in a series
190220
9Special Pythagorean triplet
189247
10Summation of primes
173710
11Largest product in a grid
129320
12Highly divisible triangular number
117939
13Large sum
124523
14Longest Collatz sequence
122492
15Lattice paths
102085
16Power digit sum
127171
17Number letter counts
84038
18Maximum path sum I
81828
19Counting Sundays
75694
20Factorial digit sum
114792
21Amicable numbers
81327
22Names scores
75867
23Non-abundant sums
57330
24Lexicographic permutations
65318
251000-digit Fibonacci number
88550
26Reciprocal cycles
46769
27Quadratic primes
49227
28Number spiral diagonals
64346
29Distinct powers
59105
30Digit fifth powers
62606
31Coin sums
46739
32Pandigital products
39976
33Digit cancelling fractions
41058
34Digit factorials
54400
35Circular primes
49615
36Double-base palindromes
52548
37Truncatable primes
42154
38Pandigital multiples
35840
39Integer right triangles
41573
40Champernowne's constant
46344
41Pandigital prime
38805
42Coded triangle numbers
44069
43Sub-string divisibility
33275
44Pentagon numbers
32051
45Triangular, pentagonal, and hexagonal
41819
46Goldbach's other conjecture
34172
47Distinct primes factors
32572
48Self powers
69046
49Prime permutations
32409
50Consecutive prime sum
34783