Composite Numbers

What Is a Composite Number?

A composite number is a number that can be divided exactly by at least one number that is not itself or 1.

This means a composite number is any number (other that 1) that is not a prime number.

For example,

  • 4 is a composite number. It can be divided exactly by 1, 2 and 4.

    4 is a composite number because it can be divided by 2 (which is not 1 or 4 itself).

  • 5 is not a composite number. It can only be divided exactly by 1 and 5.

    5 is a prime number because it can only be divided by 1 and 5 itself.

Dictionary Definition

The Oxford English Dictionary defines a composite number as "a number which is the product of two or more factors, greater than unity."

The Composite Numbers

The composite numbers are:

In a number square, the composite numbers are shaded below:

Note: This is the exact inverse of the prime numbers in a square. If this number square is overlaid with that of the prime numbers, all numbers (apart from 1) would shaded.

See Also

What is a prime number? What is a natural number? What is a factor? What is the fundamental theorem of arithmetic?