Factors of 991
The factors of 991 are 1 and 991. Since 991 is a prime number, it has exactly 2 factors and cannot be divided evenly by any other whole number. The sum of its factors is 992, and its prime factorization is simply 991 itself.
All factors of 991
Here are all 2 factors of 991, listed from smallest to largest.
Factor pairs of 991
There is only one factor pair for 991, because it is prime.
Prime factorization of 991
991 is a prime number, so it cannot be broken down further. Its prime factorization is simply 991.
Properties of 991
| Number of factors | 2 |
|---|---|
| Sum of factors | 992 |
| Sum of proper factors | 1 |
| Prime factorization | 991 |
| Prime or composite? | Prime |
| Even or odd? | Odd |
| Perfect square? | No |
| Perfect cube? | No |
| Classification | Deficient |
What makes 991 interesting
- 991 is a prime number, so its only factors are 1 and 991. It cannot be split into a product of two smaller whole numbers.
- Every prime number is deficient — the sum of its proper factors is always 1, which is far less than the number itself.
How to find the factors of 991 yourself
Divide 991 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 √991 ≈ 31.48, because every factor above that pairs with one below it.
Reading both columns gives every factor: 1, 991. The factor calculator does this automatically for any number.
Related numbers
Numbers mathematically connected to 991.
Frequently asked questions about 991
What are the factors of 991?
Is 991 a prime number?
What is the prime factorization of 991?
What two numbers multiply to give 991?
What is the sum of the factors of 991?
Is 991 a perfect square?
What is the largest factor of 991 other than itself?
How many factors does 991 have?
Explore more
Try another number in the factor calculator, break 991 down further with the prime factorization calculator, or compare 991 with another number using the GCF calculator and LCM calculator. For divisor counts and sums, see the divisor calculator.