91023721 has 16 divisors (see below), whose sum is σ = 96940800. Its totient is φ = 85333248.

The previous prime is 91023703. The next prime is 91023727. The reversal of 91023721 is 12732019.

It is a cyclic number.

It is not a de Polignac number, because 91023721 - 2⁵ = 91023689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91023727) 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, 153201 + ... + 153793.

It is an arithmetic number, because the mean of its divisors is an integer number (6058800).

Almost surely, 2^91023721 is an apocalyptic number.

It is an amenable number.

91023721 is a deficient number, since it is larger than the sum of its proper divisors (5917079).

91023721 is a wasteful number, since it uses less digits than its factorization.

91023721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 768.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 91023721 is about 9540.6352513866. The cubic root of 91023721 is about 449.8332237948.

The spelling of 91023721 in words is "ninety-one million, twenty-three thousand, seven hundred twenty-one".