91728891 has 6 divisors (see below), whose sum is σ = 132497300. Its totient is φ = 61152588.

The previous prime is 91728881. The next prime is 91728937. The reversal of 91728891 is 19882719.

It is not a de Polignac number, because 91728891 - 2⁵ = 91728859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91728881) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5096041 + ... + 5096058.

Almost surely, 2^91728891 is an apocalyptic number.

91728891 is a deficient number, since it is larger than the sum of its proper divisors (40768409).

91728891 is a wasteful number, since it uses less digits than its factorization.

91728891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10192105 (or 10192102 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 91728891 is about 9577.5200861183. The cubic root of 91728891 is about 450.9918714110.

The spelling of 91728891 in words is "ninety-one million, seven hundred twenty-eight thousand, eight hundred ninety-one".