Prime and Composite Numbers

Prime and Composite Numbers

What students learn

Students learn that a prime number has exactly two factors, 1 and itself. Start with Prime Numbers Have Only Two Factors to hear that definition clearly.

Why it matters

Knowing the difference between prime and composite numbers helps students classify numbers instead of just naming them. Composite Numbers Have More Than Two Factors shows the other side of the comparison.

Learn the idea

Once students know the definitions, they can sort examples by looking for the factor pattern. Prime and Composite Examples Reveal the Pattern gives practice with that sort.

Try it

Ask the student to test 2, 9, 11, 15, and 17. Have them name the factors for each number and explain why the number is prime or composite.

Parent guide

Keep the focus on factors, not memorized labels. If a student is unsure, ask them to list every whole-number divisor from 1 up to the number itself.