How to explain prime numbers in prime numbers to your child
22 October 2026
Prime numbers can seem tricky at first, but they follow a simple rule. When helping your child understand what makes a number prime, it helps to look at its factors one by one.
Worked example
Is 7 a prime number?
Step 1: List the factors of 7. Factors are numbers that divide 7 exactly, with no remainder.
Step 2: Try dividing 7 by each number from 1 to 7.
7 ÷ 1 = 7 (exact)
7 ÷ 2 = 3 remainder 1 (not exact)
7 ÷ 3 = 2 remainder 1 (not exact)
7 ÷ 4 = 1 remainder 3 (not exact)
7 ÷ 5 = 1 remainder 2 (not exact)
7 ÷ 6 = 1 remainder 1 (not exact)
7 ÷ 7 = 1 (exact)
Step 3: 7 can only be divided exactly by 1 and 7.
Key insight: A prime number has exactly two factors, 1 and itself.
Answer: Yes, 7 is a prime number.
| Number | 7 ÷ Number | Exact? |
|---|---|---|
| 1 | 7 | Yes |
| 2 | 3 remainder 1 | No |
| 3 | 2 remainder 1 | No |
| 4 | 1 remainder 3 | No |
| 5 | 1 remainder 2 | No |
| 6 | 1 remainder 1 | No |
| 7 | 1 | Yes |
Now your child can spot a prime number by checking if it has only two factors. This skill will help them feel more confident with similar questions in their 11+ maths practice.
