Is 24 a prime number?
24 is not a prime number. Here is the quickest way to see it.
The answer
No. 24 is not a prime number: 2 × 12 = 24.
How to see that 24 is not prime
24 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 24.
24 has 8 factors (1, 2, 3, 4, 6, 8, 12 and 24), which make 4 factor pairs.
Split 24 into prime factors
Split off the smallest prime each time, and keep going until every part is prime:
- 24 = 2 × 12
- 24 = 2 × 2 × 6
- 24 = 2 × 2 × 2 × 3
With the repeated primes written as powers, that is 2³ × 3.
24 in the times tables
24 turns up in 6 different times tables, the 2, 3, 4, 6, 8 and 12: 2 × 12, 3 × 8, 4 × 6, 6 × 4, 8 × 3 and 12 × 2.
Quick checks that catch 24
- The last digit, 4, is even, so 2 goes in.
- The digits add up to 6, which is in the 3 times table, so 3 goes in.
- Half of it is 12, which is still even, so 4 goes in.
- It is even and passes the check for 3 as well, so 6 goes in.
24 at a glance
- In words
- twenty-four
- In Roman numerals
- XXIV
- Odd or even
- Even: it ends in 4
- Its factors add up to
- 60, or 36 without 24 itself, which makes 24 an abundant number
The numbers either side of 24
- 23 is prime: 2 and 3 do not go into it, and 5 × 5 is already past 23. Check 23 in full
- 25 is not prime. 25 ends in 5, and every number ending in 5 or 0 is in the 5 times table, so 5 is a factor. Check 25 in full
Turn the digits round
24 backwards is 42. 42 is not prime. 42 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 42. Check 42 in full
Related pages
More numbers
Questions parents ask
Which prime numbers are either side of 24?
23 below it and 29 above it, a gap of 6.
What is 24 squared?
24 × 24 = 576.
What is the smallest number with as many factors as 24?
24 itself. No smaller number has 8 factors.
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.