---
tag: 0N3ADXHNTQ
kind: definition
name: Composite number
msc: [11A41]
defines: 008BH74D7R
uses: [0SN0MAEKYX]
sources:
  - url: https://en.wikipedia.org/wiki/Composite_number
    locator: lead section
---

## Definition

A composite number is a natural number $n$ such that $n > 1$ and $n$ is not a [[prime number|0SN0MAEKYX]].

## Remarks

Equivalently, $n$ is composite when $n = a b$ for some natural numbers $a$ and $b$ with $1 < a < n$ and $1 < b < n$.
The first composite numbers are $4, 6, 8, 9, 10, 12$.
The number $1$ is neither prime nor composite.

## Explanations

### L1 human

A composite number is a number that you can write as a product of two smaller numbers, each greater than $1$.
For example, $15 = 3 \cdot 5$ is composite.
You can arrange a composite number of dots as a rectangle with at least two rows and at least two columns.