91091920 has 20 divisors (see below), whose sum is σ = 211788900. Its totient is φ = 36436736.

The previous prime is 91091887. The next prime is 91091921. The reversal of 91091920 is 2919019.

It can be written as a sum of positive squares in 2 ways, for example, as 27793984 + 63297936 = 5272^2 + 7956^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91091921) 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, 569245 + ... + 569404.

It is an arithmetic number, because the mean of its divisors is an integer number (10589445).

Almost surely, 2^91091920 is an apocalyptic number.

It is an amenable number.

91091920 is an abundant number, since it is smaller than the sum of its proper divisors (120696980).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

91091920 is a wasteful number, since it uses less digits than its factorization.

91091920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1138662 (or 1138656 counting only the distinct ones).

The product of its (nonzero) digits is 1458, while the sum is 31.

The square root of 91091920 is about 9544.2087152367. The cubic root of 91091920 is about 449.9455407347.

The spelling of 91091920 in words is "ninety-one million, ninety-one thousand, nine hundred twenty".