Prime And Composite Numbers Worksheets

Prime and composite numbers help students understand how numbers are built. In this section, students practice identifying whether a number is prime, composite, or neither by examining its factors. These worksheets focus on listing all factors of a number and using that information to make accurate classifications. This skill supports multiplication, division, and future topics like greatest common factor (GCF) and least common multiple (LCM).

Free printable prime and composite numbers worksheet for 3rd grade where students list all factors of each number and decide whether it is prime, composite, or neither, including examples with the number 1.

Prime and Composite Numbers Worksheet: Find the Factors

3rd Grade4th Grade

Prime & Composite NumbersFactors & Multiples

A prime number worksheet that shows an image of a plane ticket and asks students to find prime numbers.

Now Boarding: Fun Prime Numbers Worksheet

4th Grade5th Grade

Factors & MultiplesPrime & Composite Numbers

Understanding the difference between prime and composite numbers begins with a strong grasp of factors. A prime number has exactly two factors: 1 and itself. A composite number has more than two factors, meaning it can be broken down into multiple factor pairs. The number 1 is a special case because it has only one factor, so it is neither prime nor composite.

The prime and composite numbers worksheets on this page guide students through this reasoning step by step. Students are asked to list all factors of a number before deciding how it should be classified. This approach encourages careful thinking and reduces common mistakes, such as mislabeling numbers that appear “large” or assuming all odd numbers are prime.

These worksheets are designed primarily for 3rd grade math, with many also suitable for early 4th grade review or intervention. By practicing factor identification alongside classification, students build number sense that directly supports later skills, including simplifying fractions, finding common factors, and understanding number patterns.

Teachers and parents can use these printable worksheets for independent practice, small groups, math centers, or homework. Answer keys are included to make checking work quick and easy. Whether students are learning this concept for the first time or reviewing it, these activities provide clear, focused practice with prime and composite numbers.

Learn More About Prime & Composite Numbers

What is a prime number?

A prime number is a whole number greater than 1 that has exactly two factors: 1 and itself. Examples include 2, 3, 5, 7, and 11.

What is a composite number?

A composite number is a whole number greater than 1 that has more than two factors. For example, 12 is composite because it has the factors 1, 2, 3, 4, 6, and 12.

Why is the number 1 neither prime nor composite?

The number 1 has only one factor, which is itself. Since prime numbers must have exactly two factors and composite numbers must have more than two, 1 does not fit either category.

How can students tell if a number is prime or composite?

Students can list all the factors of a number. If there are only two factors, the number is prime. If there are more than two factors, the number is composite.

Why is this skill important?

Knowing whether a number is prime or composite helps students:

  • understand multiplication and division relationships

  • prepare for greatest common factor (GCF) and least common multiple (LCM)

  • build strong number sense for later math topics

What grade level is this skill best for?

Prime and composite numbers are typically introduced in 3rd grade. Many of these worksheets are also useful for 4th grade review, small-group instruction, or math intervention.