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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 start color #1fab54, 1, end color #1fab54 and the number start color #7854ab, start text, i, t, s, e, l, f, end text, end color #7854ab.
7 is an example of a prime number. Its only factors are start color #1fab54, 1, end color #1fab54 and start color #7854ab, 7, end color #7854ab. It is not evenly divisible by any other whole numbers.

## Practice set 1: Identifying prime numbers

Problem 1A
• Current
Which of these numbers is prime?
12, comma, space, 42, comma, space, 61, comma, space, 87, comma, space, 95

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 start text, i, t, s, e, l, f, end text.
16 is an example of a composite number. The factors of 16 are 1, comma, 2, comma, 4, comma, 8 and 16, point All of these numbers divide into 16 evenly.