91231920 has 360 divisors, whose sum is σ = 361133136. Its totient is φ = 21275136.

The previous prime is 91231919. The next prime is 91231927. The reversal of 91231920 is 2913219.

It is a tau number, because it is divible by the number of its divisors (360).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (91231927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 4801671 + ... + 4801689.

Almost surely, 2^91231920 is an apocalyptic number.

91231920 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 91231920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (180566568).

91231920 is an abundant number, since it is smaller than the sum of its proper divisors (269901216).

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

91231920 is a wasteful number, since it uses less digits than its factorization.

91231920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79 (or 42 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 91231920 is about 9551.5401899380. The cubic root of 91231920 is about 450.1759312093.

The spelling of 91231920 in words is "ninety-one million, two hundred thirty-one thousand, nine hundred twenty".