91991680 has 128 divisors (see below), whose sum is σ = 244555200. Its totient is φ = 32808960.

The previous prime is 91991671. The next prime is 91991681. The reversal of 91991680 is 8619919.

It is a tau number, because it is divible by the number of its divisors (128).

It is not an unprimeable number, because it can be changed into a prime (91991681) 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, 513831 + ... + 514009.

Almost surely, 2^91991680 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 91991680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (122277600).

91991680 is an abundant number, since it is smaller than the sum of its proper divisors (152563520).

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

91991680 is a wasteful number, since it uses less digits than its factorization.

91991680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 282 (or 270 counting only the distinct ones).

The product of its (nonzero) digits is 34992, while the sum is 43.

The square root of 91991680 is about 9591.2293268381. The cubic root of 91991680 is about 451.4221346394.

The spelling of 91991680 in words is "ninety-one million, nine hundred ninety-one thousand, six hundred eighty".