91811231 has 4 divisors (see below), whose sum is σ = 91933272. Its totient is φ = 91689192.

The previous prime is 91811227. The next prime is 91811261. The reversal of 91811231 is 13211819.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 91811231 - 2² = 91811227 is a prime.

It is a super-2 number, since 2×91811231² = 16858604275470722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 91811231.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91811201) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 59885 + ... + 61398.

It is an arithmetic number, because the mean of its divisors is an integer number (22983318).

Almost surely, 2^91811231 is an apocalyptic number.

91811231 is a deficient number, since it is larger than the sum of its proper divisors (122041).

91811231 is a wasteful number, since it uses less digits than its factorization.

91811231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 122040.

The product of its digits is 432, while the sum is 26.

The square root of 91811231 is about 9581.8177294290. The cubic root of 91811231 is about 451.1267746190.

The spelling of 91811231 in words is "ninety-one million, eight hundred eleven thousand, two hundred thirty-one".