91761577981 has 2 divisors, whose sum is σ = 91761577982. Its totient is φ = 91761577980.

The previous prime is 91761577967. The next prime is 91761578017. The reversal of 91761577981 is 18977516719.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 90666629881 + 1094948100 = 301109^2 + 33090^2 .

It is a cyclic number.

It is not a de Polignac number, because 91761577981 - 2⁵ = 91761577949 is a prime.

It is a super-2 number, since 2×91761577981² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91761577381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45880788990 + 45880788991.

It is an arithmetic number, because the mean of its divisors is an integer number (45880788991).

Almost surely, 2^91761577981 is an apocalyptic number.

It is an amenable number.

91761577981 is a deficient number, since it is larger than the sum of its proper divisors (1).

91761577981 is an equidigital number, since it uses as much as digits as its factorization.

91761577981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6667920, while the sum is 61.

The spelling of 91761577981 in words is "ninety-one billion, seven hundred sixty-one million, five hundred seventy-seven thousand, nine hundred eighty-one".