4th Grade Prime and Composite Numbers Worksheet
Tell whether each number is prime (exactly two factors) or composite (more than two).
- Homework
- Review
- Test Prep
- Tutoring
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- Grade
- 4th Grade
- Subject
- Math
- Skill
- Factors & Multiples
- Topic
- prime and composite numbers
- Difficulty
- Standard
- Time
- 15 minutes
- Pages
- 2 (incl. answer key)
- Format
- Printable PDF (US Letter)
- Answer key
- Included
- Best for
- homework, review, test prep, tutoring
Worksheet details
What This Worksheet Practices
Students will classify whole numbers as prime or composite by counting their factors.
- Counting a number's factors
- Classifying numbers as prime or composite
- Knowing 1 is neither
Worksheet Preview
Counting factors to classify
The difference comes down to counting factors: a prime number has exactly two (1 and itself), while a composite number has more than two. So 7 is prime (just 1 and 7), but 9 is composite (1, 3, 9). Two facts students forget: 1 is neither, and not all odd numbers are prime (9 and 15 are composite).
How to use it
Have students list the factors of each number, then count them. Two factors means prime; more means composite. This builds directly on factors and multiples.
👩🏫 Teacher note
A prime number has exactly two factors: 1 and itself. A composite number has more than two. Remind students that 1 is neither, and that odd does not mean prime (9 = 3 x 3).
🏠 Parent note
If a number's only factors are 1 and itself, it's prime. If it has others, it's composite.
Common Mistakes to Watch For
- Calling 1 prime (it is neither)
- Assuming all odd numbers are prime (9 and 15 are not)
Answer Key
Each answer says prime or composite.
⬇ Download Answer Key (PDF)Related Worksheets
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