Is 80 a prime number?
80 is not a prime number. Here is the quickest way to see it.
The answer
No. 80 is not a prime number: 2 × 40 = 80.
How to see that 80 is not prime
80 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 80.
80 has 10 factors (1, 2, 4, 5, 8, 10, 16, 20, 40 and 80), which make 5 factor pairs.
Split 80 into prime factors
Split off the smallest prime each time, and keep going until every part is prime:
- 80 = 2 × 40
- 80 = 2 × 2 × 20
- 80 = 2 × 2 × 2 × 10
- 80 = 2 × 2 × 2 × 2 × 5
With the repeated primes written as powers, that is 2⁴ × 5.
80 in the times tables
80 turns up in 2 different times tables, the 8 and 10: 8 × 10 and 10 × 8.
Quick checks that catch 80
- The last digit, 0, is even, so 2 goes in.
- Half of it is 40, which is still even, so 4 goes in.
- It ends in 0, so 5 goes in.
- It ends in 0, so 10 goes in.
80 at a glance
- In words
- eighty
- In Roman numerals
- LXXX
- Odd or even
- Even: it ends in 0
- Multiple of 10
- 8 tens
- Its factors add up to
- 186, or 106 without 80 itself, which makes 80 an abundant number
The numbers either side of 80
- 79 is prime: 2, 3, 5 and 7 do not go into it, and 11 × 11 is already past 79. Check 79 in full
- 81 is not prime. Its digits add up to 8 + 1 = 9, which is a multiple of 3. That means 81 is a multiple of 3 too, so 3 is a factor. Check 81 in full
Related pages
More numbers
Questions parents ask
Which prime numbers are either side of 80?
79 below it and 83 above it, a gap of 4.
What is 80 squared?
80 × 80 = 6400.
What is the smallest number with as many factors as 80?
48. It has 10 factors, the same as 80.
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.