• Index
• Keywords
• Home
• Random
• Glossary

• Previous
• Next
• Random

• Mail Editor
• Submit Curio
• Prime Puzzio
• Test Number

It is unknown if there is a relatively prime pair of amicable numbers. If there is such a pair, their product must be at least 22 distinct primes.

The smallest integer such that its sum of digits + 1 and the product of its digits is prime, together with the fact that the sum of digits is the same as the product. [Russo]

22 is the smallest number which can be expressed as the sum of two primes in three ways. [Murthy]

1⁽¹⁾ + 2⁽²⁾ + 3⁽³⁾ + 4⁽⁴⁾ + ... + 22⁽²²⁾ is prime. [Poo Sung]

The smallest multi-digit square-free number such that all the digits are primes. [Russo]

The smallest multi-digit composite palindrome whose total number of prime factors (counting multiplicity) is square-free. [Russo]

The longest known arithmetic sequence of primes is currently 22, starting with the prime 11410337850553 and continuing with common difference 4609098694200 (found by Pritchard, Moran, and Thyssen in 1993).

22 is the smallest multidigit composite palindrome such that the concatenation (211) as well as the sum (13) of its prime factors are prime. [De Geest]

It is possible for a Queen to attack all 22 prime numbered squares on 9x9 Knight's Tour solution (Jacques Tramu, 2004).

22 is the smallest Hoax Number.

The smallest dihedral semiprime. Note that it contains the smallest dihedral prime. [Capelle]