91327721665 has 12 divisors (see below), whose sum is σ = 111419352252. Its totient is φ = 71864422080.

The previous prime is 91327721633. The next prime is 91327721741. The reversal of 91327721665 is 56612772319.

It can be written as a sum of positive squares in 6 ways, for example, as 55983345664 + 35344376001 = 236608^2 + 188001^2 .

It is not a de Polignac number, because 91327721665 - 2⁵ = 91327721633 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2435782 + ... + 2472991.

It is an arithmetic number, because the mean of its divisors is an integer number (9284946021).

Almost surely, 2^91327721665 is an apocalyptic number.

It is an amenable number.

91327721665 is a deficient number, since it is larger than the sum of its proper divisors (20091630587).

91327721665 is an equidigital number, since it uses as much as digits as its factorization.

91327721665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4908900 (or 4908839 counting only the distinct ones).

The product of its digits is 952560, while the sum is 49.

The spelling of 91327721665 in words is "ninety-one billion, three hundred twenty-seven million, seven hundred twenty-one thousand, six hundred sixty-five".