Is 80 a prime number?
80 is not a prime number. Here is a way to check 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 repeated primes written as powers, that is 2⁴ × 5. A small raised number tells you how many times to use that factor: for example, 2³ means 2 × 2 × 2.
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
Optional extra number facts:
- 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. 80 is abundant: Abundant means this sum is greater than the 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.
Continue your number practice
Explore the diagnostic for another set of practice questions.