91581891 has 8 divisors (see below), whose sum is σ = 122179584. Its totient is φ = 61019400.

The previous prime is 91581877. The next prime is 91581899. The reversal of 91581891 is 19818519.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 91581891 - 2¹⁸ = 91319747 is a prime.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (91581899) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1971 + ... + 13676.

It is an arithmetic number, because the mean of its divisors is an integer number (15272448).

Almost surely, 2^91581891 is an apocalyptic number.

91581891 is the 6053-rd centered pentagonal number.

91581891 is a deficient number, since it is larger than the sum of its proper divisors (30597693).

91581891 is a wasteful number, since it uses less digits than its factorization.

91581891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17601.

The product of its digits is 25920, while the sum is 42.

The square root of 91581891 is about 9569.8427886774. The cubic root of 91581891 is about 450.7508304841.

The spelling of 91581891 in words is "ninety-one million, five hundred eighty-one thousand, eight hundred ninety-one".