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Lesson 2: Prime and composite numbers

# Prime and composite numbers review

Review prime and composite numbers, and try some practice problems.

## What are prime numbers?

Prime numbers are numbers with exactly $2$ factors.
A prime number's only factors are $1$ and the number $\text{itself}$.
$7$ is an example of a prime number. Its only factors are $1$ and $7$. It is not evenly divisible by any other whole numbers.

## Practice set 1: Identifying prime numbers

Problem 1A
Which of these numbers is prime?

Want to try more problems like this? Check out this exercise.

## What are composite numbers?

Composite numbers have more than $2$ factors. A composite number has factors in addition to $1$ and the number $\text{itself}$.
$16$ is an example of a composite number. The factors of $16$ are $1,2,4,8$ and $16.$ All of these numbers divide into $16$ evenly.