91231921 has 8 divisors (see below), whose sum is σ = 101404224. Its totient is φ = 81372720.

The previous prime is 91231919. The next prime is 91231927. The reversal of 91231921 is 12913219.

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

It is not a de Polignac number, because 91231921 - 2¹ = 91231919 is a prime.

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 91231921.

It is not an unprimeable number, because it can be changed into a prime (91231927) 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, 77661 + ... + 78826.

It is an arithmetic number, because the mean of its divisors is an integer number (12675528).

Almost surely, 2^91231921 is an apocalyptic number.

It is an amenable number.

91231921 is a deficient number, since it is larger than the sum of its proper divisors (10172303).

91231921 is a wasteful number, since it uses less digits than its factorization.

91231921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 156551.

The product of its digits is 972, while the sum is 28.

The square root of 91231921 is about 9551.5402422855. The cubic root of 91231921 is about 450.1759328541.

The spelling of 91231921 in words is "ninety-one million, two hundred thirty-one thousand, nine hundred twenty-one".