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Problems Archives

The problems archives table shows problems 1 to 682. 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
902281
2Even Fibonacci numbers
719020
3Largest prime factor
513806
4Largest palindrome product
454384
5Smallest multiple
459622
6Sum square difference
462653
710001st prime
395132
8Largest product in a series
330364
9Special Pythagorean triplet
335364
10Summation of primes
306790
11Largest product in a grid
219701
12Highly divisible triangular number
206438
13Large sum
212022
14Longest Collatz sequence
212048
15Lattice paths
174742
16Power digit sum
214378
17Number letter counts
141389
18Maximum path sum I
135429
19Counting Sundays
125976
20Factorial digit sum
186007
21Amicable numbers
136495
22Names scores
125399
23Non-abundant sums
96672
24Lexicographic permutations
106957
251000-digit Fibonacci number
145499
26Reciprocal cycles
77794
27Quadratic primes
81064
28Number spiral diagonals
101201
29Distinct powers
98032
30Digit fifth powers
102509
31Coin sums
78735
32Pandigital products
65850
33Digit cancelling fractions
66407
34Digit factorials
87732
35Circular primes
78755
36Double-base palindromes
82873
37Truncatable primes
68217
38Pandigital multiples
58223
39Integer right triangles
67740
40Champernowne's constant
74494
41Pandigital prime
63019
42Coded triangle numbers
69157
43Sub-string divisibility
55099
44Pentagon numbers
53803
45Triangular, pentagonal, and hexagonal
66023
46Goldbach's other conjecture
56781
47Distinct primes factors
53492
48Self powers
105480
49Prime permutations
53440
50Consecutive prime sum
57679