91991280 has 40 divisors (see below), whose sum is σ = 285173712. Its totient is φ = 24530944.

The previous prime is 91991279. The next prime is 91991281. The reversal of 91991280 is 8219919.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (91991279) and next prime (91991281).

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91991281) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 191409 + ... + 191888.

Almost surely, 2^91991280 is an apocalyptic number.

It is an amenable number.

91991280 is an abundant number, since it is smaller than the sum of its proper divisors (193182432).

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

91991280 is a wasteful number, since it uses less digits than its factorization.

91991280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 383313 (or 383307 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 39.

The square root of 91991280 is about 9591.2084744312. The cubic root of 91991280 is about 451.4214803443.

The spelling of 91991280 in words is "ninety-one million, nine hundred ninety-one thousand, two hundred eighty".