Is 7 a prime number?
7 is a prime number. Here is how to check it, one division at a time.
The answer
Yes. 7 is a prime number: its only factors are 1 and 7.
How to check that 7 is prime
Try dividing 7 by the prime numbers, starting with 2. You only need primes: if 4 went into 7, then 2 would too.
- 7 ÷ 2 = 3 remainder 1, so 2 is not a factor.
Stop at 3: 3 × 3 = 9, which is more than 7. Any factor bigger than that would need a partner smaller than 3, and you have already tried those. So 7 is prime.
Where 7 comes among the primes
7 is the 4th prime number. The prime just before it is 5.
There are 25 prime numbers up to 100: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97.
Around 7
- 7 is in only one times table, its own, as 7 × 1. The next answer in it is 7 × 2 = 14.
- The nearest square number is 9 (3 × 3), 2 above it.
- Primes 4 apart are called cousin primes, and 7 has two cousins: 3 and 11.
7 at a glance
- In words
- seven
- In Roman numerals
- VII
- Odd or even
- Odd: it ends in 7
- Its factors add up to
- 8, or 1 without 7 itself, which makes 7 a deficient number
Related pages
More numbers
Questions parents ask
Is 7 one of a pair of twin primes?
Yes. Twin primes are two primes 2 apart, and 7 pairs with 5.
What is the next prime number after 7?
11, which is 4 more than 7. Every number in between has a factor other than 1 and itself.
What is 7 × 7?
7 × 7 = 49. The square of a prime has exactly three factors: 1, 7 and 49.
Number facts are the base of 11+ maths
Factors, multiples, primes and square numbers come up all over 11+ maths, from simplifying fractions to ratio. The free diagnostic checks maths, English and both kinds of reasoning, and shows what to practise next. No card is required.