Is 39 a prime number?
39 is not a prime number. Here is the quickest way to see it.
The answer
No. 39 is not a prime number: 3 × 13 = 39.
How to see that 39 is not prime
Its digits add up to 3 + 9 = 12, which is a multiple of 3. That means 39 is a multiple of 3 too, so 3 is a factor.
39 has four factors: 1 and 39, plus one pair in between, 3 and 13.
Split 39 into prime factors
39 splits straight into two primes, 3 × 13, so its factor tree has only one branch.
39 in the times tables
No fact from the 2 to 12 times tables, up to × 12, makes 39. Its smallest pair, 3 × 13, needs the 13 times table, which goes past 12.
See the 13 times table, where 13 × 3 = 39 is one of the facts.
Quick checks that catch 39
- The digits add up to 12, which is in the 3 times table, so 3 goes in.
39 at a glance
- In words
- thirty-nine
- In Roman numerals
- XXXIX
- Odd or even
- Odd: it ends in 9
- Its factors add up to
- 56, or 17 without 39 itself, which makes 39 a deficient number
The numbers either side of 39
- 38 is not prime. 38 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 38. Check 38 in full
- 40 is not prime. 40 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 40. Check 40 in full
Turn the digits round
39 backwards is 93. 93 is not prime. Its digits add up to 9 + 3 = 12, which is a multiple of 3. That means 93 is a multiple of 3 too, so 3 is a factor. Check 93 in full
Related pages
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Questions parents ask
Which prime numbers are either side of 39?
37 below it and 41 above it, a gap of 4.
What is 39 squared?
39 × 39 = 1521.
What is the smallest number with as many factors as 39?
6. It has 4 factors, the same as 39.
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.