91169777981 has 2 divisors, whose sum is σ = 91169777982. Its totient is φ = 91169777980.

The previous prime is 91169777971. The next prime is 91169777983. The reversal of 91169777981 is 18977796119.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 83602517881 + 7567260100 = 289141^2 + 86990^2 .

It is a cyclic number.

It is not a de Polignac number, because 91169777981 - 2¹⁸ = 91169515837 is a prime.

It is a super-2 number, since 2×91169777981² (a number of 23 digits) contains 22 as substring.

Together with 91169777983, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91169777983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45584888990 + 45584888991.

It is an arithmetic number, because the mean of its divisors is an integer number (45584888991).

Almost surely, 2^91169777981 is an apocalyptic number.

It is an amenable number.

91169777981 is a deficient number, since it is larger than the sum of its proper divisors (1).

91169777981 is an equidigital number, since it uses as much as digits as its factorization.

91169777981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12002256, while the sum is 65.

The spelling of 91169777981 in words is "ninety-one billion, one hundred sixty-nine million, seven hundred seventy-seven thousand, nine hundred eighty-one".