Composite number

A composite number is a positive integer that can be factored as a product of two or more prime numbers. Every integer except one and zero is either a prime number or a composite number. The integer 14 is a composite number because it can be factored as 2 × 7.

Properties

• All even numbers greater than 2 are composite numbers.
• All composite numbers are non-primes.
• The smallest composite number is 4.
• One has <math>(n-1)! + 1\,\,\, \not\equiv \,\, 0 \pmod{n}<math> for all composite numbers <math>n\,\!<math> greater than 4 (Wilson's theorem).
• Also, <math>(n-1)! \,\,\, \equiv \,\, 0 \pmod{n}<math> for all composite numbers <math>n\,\!<math> greater than 4 (composite theorem).