Problem Archives

The problems archives table shows problems 1 to 997. If you would like to tackle the 10 most recently published problems, go to Recent problems.

ID	Title	Solved By
1	Multiples of 3 or 5	861663
2	Even Fibonacci Numbers	688622
3	Largest Prime Factor	518145
4	Largest Palindrome Product	457815
5	Smallest Multiple	444217
6	Sum Square Difference	449147
7	10 001st Prime	391316
8	Largest Product in a Series	332725
9	Special Pythagorean Triplet	338470
10	Summation of Primes	317618
11	Largest Product in a Grid	237521
12	Highly Divisible Triangular Number	233784
13	Large Sum	234481
14	Longest Collatz Sequence	238878
15	Lattice Paths	202476
16	Power Digit Sum	237049
17	Number Letter Counts	169717
18	Maximum Path Sum I	163952
19	Counting Sundays	153791
20	Factorial Digit Sum	207001
21	Amicable Numbers	169063
22	Names Scores	155754
23	Non-Abundant Sums	128246
24	Lexicographic Permutations	137457
25	$1000$-digit Fibonacci Number	175347
26	Reciprocal Cycles	104414
27	Quadratic Primes	107933
28	Number Spiral Diagonals	126646
29	Distinct Powers	127683
30	Digit Fifth Powers	132414
31	Coin Sums	104269
32	Pandigital Products	88823
33	Digit Cancelling Fractions	88623
34	Digit Factorials	114761
35	Circular Primes	102866
36	Double-base Palindromes	107330
37	Truncatable Primes	90795
38	Pandigital Multiples	78020
39	Integer Right Triangles	89720
40	Champernowne's Constant	96824
41	Pandigital Prime	84169
42	Coded Triangle Numbers	89700
43	Sub-string Divisibility	74131
44	Pentagon Numbers	72718
45	Triangular, Pentagonal, and Hexagonal	86147
46	Goldbach's Other Conjecture	76262
47	Distinct Primes Factors	71750
48	Self Powers	122960
49	Prime Permutations	71360
50	Consecutive Prime Sum	76454