Prime or Composite?

These free printable prime and composite worksheets are ideal for 5th graders learning to classify numbers by their factors. The numbers are chosen to include the classic composites in disguise - 51, 57, and 91 - that catch students who guess from looks alone.

How to Solve Factors & Multiples

A prime number has exactly two factors: 1 and itself. Test each number with the small primes in order: is it even (divisible by 2), do its digits add to a multiple of 3, does it end in 0 or 5, and does 7 divide it? If every test fails, the number is prime. Remember that 2 is the only even prime.

You can view the preview of this worksheet below, or download the full high-resolution PDF along with the answer key for easy grading.