BIGpedia - Composite number - Encyclopedia and Dictionary Online

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 $(n-1)! + 1\,\,\, \not\equiv \,\, 0 \pmod{n}$ for all composite numbers $n\,\!$ greater than 4 (Wilson's theorem).
Also, $(n-1)! \,\,\, \equiv \,\, 0 \pmod{n}$ for all composite numbers $n\,\!$ greater than 4 (composite theorem).

Categories: Elementary arithmetic | Prime numbers

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01-04-2007 01:21:04