91561988 has 72 divisors (see below), whose sum is σ = 204926400. Its totient is φ = 35525952.

The previous prime is 91561913. The next prime is 91561991. The reversal of 91561988 is 88916519.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 85118 + ... + 86186.

It is an arithmetic number, because the mean of its divisors is an integer number (2846200).

Almost surely, 2^91561988 is an apocalyptic number.

91561988 is a gapful number since it is divisible by the number (98) 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 91561988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (102463200).

91561988 is an abundant number, since it is smaller than the sum of its proper divisors (113364412).

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

91561988 is a wasteful number, since it uses less digits than its factorization.

91561988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1129 (or 1120 counting only the distinct ones).

The product of its digits is 155520, while the sum is 47.

The square root of 91561988 is about 9568.8028509318. The cubic root of 91561988 is about 450.7181750335.

The spelling of 91561988 in words is "ninety-one million, five hundred sixty-one thousand, nine hundred eighty-eight".