What is a Composite Number?
A number with three or more factors
A composite number is a whole number that has more than two factors. This means that we can divide it evenly by numbers other than just 1 and itself.
Examples of composite numbers include:
- 4 is composite because we can divide it evenly by 1, 2, and 4
- 9 is composite because we can divide it by 1, 3, and 9
- 12 is composite because it has lots of factors: 1, 2, 3, 4, 6, and 12
Is 1 a composite number?
No, because it can only be divided by 1 and itself. The same is true for numbers like 3, 5, and 7, so we can say that these are not composite.
We use composite numbers to help us understand multiplication, division, and factoring. They’re the opposite of prime numbers, which only have two distinct factors: 1 and themselves.
When Do Students Learn About Composite Numbers?
Students typically learn about composite numbers when they study factors and multiples, often alongside prime numbers.
Grades 4–5 – Introduction to Prime and Composite Numbers
Students learn to list factors of numbers and decide whether a number is prime or composite.
Grades 6+ – Factors and Multiples in Depth
Students use composite numbers in problems involving greatest common factors (GCF), least common multiples (LCM), and prime factorization.
