Prime and Composite Numbers

Prime and Composite Numbers

What students learn

Students learn that prime numbers have exactly two factors, 1 and the number itself, while composite numbers have more than two factors. Start with Prime Numbers Have Exactly Two Factors to hear the definition, then use Composite Numbers Have More Than Two Factors to hear the contrast.

Why it matters

Once students can sort prime and composite numbers, they can talk about numbers with more precision. Prime and Composite Examples Build a Sorting Habit helps them build that habit by checking factors instead of guessing.

Learn the idea

A prime number has only one factor pair: 1 and itself. A composite number has at least one extra factor pair. That difference gives students a clean way to classify numbers and explain their thinking out loud.

Try it

Ask the student to test 2, 4, 9, 11, 15, and 17. Have them list the factors for each number and say whether the number is prime or composite.

Parent guide

Keep the conversation focused on factors. If the student is unsure, ask them to write every whole-number divisor from 1 up to the number itself and circle the pairs that match.