Is 54 a prime number?
54 is not a prime number. Here is the quickest way to see it.
The answer
No. 54 is not a prime number: 2 × 27 = 54.
How to see that 54 is not prime
54 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 54.
54 has 8 factors (1, 2, 3, 6, 9, 18, 27 and 54), which make 4 factor pairs.
Split 54 into prime factors
Split off the smallest prime each time, and keep going until every part is prime:
- 54 = 2 × 27
- 54 = 2 × 3 × 9
- 54 = 2 × 3 × 3 × 3
With the repeated primes written as powers, that is 2 × 3³.
54 in the times tables
54 turns up in 2 different times tables, the 6 and 9: 6 × 9 and 9 × 6.
Quick checks that catch 54
- The last digit, 4, is even, so 2 goes in.
- The digits add up to 9, which is in the 3 times table, so 3 goes in.
- It is even and passes the check for 3 as well, so 6 goes in.
- The digit total, 9, is a multiple of 9, so 9 goes in.
54 at a glance
- In words
- fifty-four
- In Roman numerals
- LIV
- Odd or even
- Even: it ends in 4
- Its factors add up to
- 120, or 66 without 54 itself, which makes 54 an abundant number
The numbers either side of 54
- 53 is prime: 2, 3, 5 and 7 do not go into it, and 11 × 11 is already past 53. Check 53 in full
- 55 is not prime. 55 ends in 5, and every number ending in 5 or 0 is in the 5 times table, so 5 is a factor. Check 55 in full
Turn the digits round
54 backwards is 45. 45 is not prime. Its digits add up to 4 + 5 = 9, which is a multiple of 3. That means 45 is a multiple of 3 too, so 3 is a factor. Check 45 in full
Related pages
More numbers
Questions parents ask
Which prime numbers are either side of 54?
53 below it and 59 above it, a gap of 6.
What is 54 squared?
54 × 54 = 2916.
What is the smallest number with as many factors as 54?
24. It has 8 factors, the same as 54.
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.