Factors of 391
The factors of 391 are 1, 17, 23, and 391. In total, 391 has 4 factors. Its prime factorization is 17 × 23, and the sum of all its factors is 432.
All factors of 391
Here are all 4 factors of 391, listed from smallest to largest.
Factor pairs of 391
These 2 pairs of whole numbers each multiply to give 391.
Prime factorization of 391
Dividing 391 by the smallest prime at each step gives its prime factorization:
The distinct prime factors of 391 are 17, 23. To factorize any other number, use the prime factorization calculator.
Factor tree of 391
A factor tree shows the same prime factorization visually. Each composite branch splits until every endpoint is a prime number.
Properties of 391
| Number of factors | 4 |
|---|---|
| Sum of factors | 432 |
| Sum of proper factors | 41 |
| Prime factorization | 17 × 23 |
| Prime or composite? | Composite |
| Even or odd? | Odd |
| Perfect square? | No |
| Perfect cube? | No |
| Classification | Deficient |
What makes 391 interesting
- 391 is a composite number, meaning it has more than two factors. It can be written as a product of smaller whole numbers in 2 different ways.
- 391 is a deficient number: its proper factors sum to 41, which is 350 less than 391 itself.
How to find the factors of 391 yourself
Divide 391 by each whole number starting from 1. Whenever the division leaves no remainder, both the divisor and the quotient are factors. You only need to test up to √391 ≈ 19.77, because every factor above that pairs with one below it.
Reading both columns gives every factor: 1, 17, 23, 391. The factor calculator does this automatically for any number.
Related numbers
Numbers mathematically connected to 391.
Frequently asked questions about 391
What are the factors of 391?
Is 391 a prime number?
What is the prime factorization of 391?
What two numbers multiply to give 391?
What is the sum of the factors of 391?
Is 391 a perfect square?
What is the largest factor of 391 other than itself?
How many factors does 391 have?
Explore more
Try another number in the factor calculator, break 391 down further with the prime factorization calculator, or compare 391 with another number using the GCF calculator and LCM calculator. For divisor counts and sums, see the divisor calculator.