991 is a prime number from 901-1000. 991 is the 167th prime number, and the thirteenth prime number from 901-1000.
Proofs[]
— 991 is divisible by 1.
— 991 is not divisible by 2-990.
- — 991 is divisible by 991.
Relationship with other odd numbers[]
The numbers before[]
- The previous prime number is 983, 8 numbers away.
The numbers after[]
- The next prime number is 997.
- 991 and 997 are sexy primes.
Trivia[]
- 991, 99991, and 9999991 are all prime.
- This number, 331 and 661 are all prime. Note that the product of these three primes is 216,821,881 which is a Carmichael Number.
- The largest three-digit permutable prime.
- 991^2 = 982081 and 982 + 0 + 8 + 1 = 991.
- The last permutable prime number, which is not also a repunit prime. Next numbers is impossible because combinatorics does not allow permuting other digits in such a way that in every possible way there is a prime number, and prime numbers are becoming more and more rare.