Factors of 81
The factors of 81 are 1, 3, 9, 27, 81. It has 5 factors.
Factors of 81
Pick any whole number from 1 to 10,000.
How to work it out
- 1
A factor of 81 is a whole number that divides it with nothing left over. You only need to test the numbers up to √81 ≈ 9.00; every one that divides gives a pair.
- 2
The factor pairs are listed in the table below. Together they give 5 factors.
- 3
Prime factorisation: keep dividing by the smallest prime that fits.
- 4
Add all the factors: 1 + 3 + 9 + 27 + 81 = 121. Without 81 itself that is 40, so 81 is a deficient number.
LaTeX source of the formulas on this page
\[ 81 = 3^{4} \]Factor pairs of 81
| Factor | Pairs with | Product |
|---|---|---|
| 1 | 81 | 1 × 81 = 81 |
| 3 | 27 | 3 × 27 = 81 |
| 9 | 9 | 9 × 9 = 81 |
Questions
What are the factors of 81?
The factors of 81 are 1, 3, 9, 27, 81. It has 5 factors.
What are the prime factors of 81?
3. As a product: .
How many factors does 81 have?
81 has 5 factors (3 factor pairs, one of them 9 × 9).
What is the sum of the factors of 81?
121.
Is 81 a prime number?
No. It is divisible by 3, so 81 = 3 × 27.