91320021 has 16 divisors (see below), whose sum is σ = 145696320. Its totient is φ = 56196720.

The previous prime is 91320011. The next prime is 91320037. The reversal of 91320021 is 12002319.

It is a happy number.

It is not a de Polignac number, because 91320021 - 2²¹ = 89222869 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 91319976 and 91320003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91320011) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 129735 + ... + 130436.

It is an arithmetic number, because the mean of its divisors is an integer number (9106020).

Almost surely, 2^91320021 is an apocalyptic number.

It is an amenable number.

91320021 is a deficient number, since it is larger than the sum of its proper divisors (54376299).

91320021 is a wasteful number, since it uses less digits than its factorization.

91320021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 260193 (or 260187 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 18.

The square root of 91320021 is about 9556.1509510890. The cubic root of 91320021 is about 450.3207934824.

The spelling of 91320021 in words is "ninety-one million, three hundred twenty thousand, twenty-one".