91987971 has 16 divisors (see below), whose sum is σ = 132399360. Its totient is φ = 56635040.

The previous prime is 91987963. The next prime is 91987979. The reversal of 91987971 is 17978919.

It is an interprime number because it is at equal distance from previous prime (91987963) and next prime (91987979).

It is a cyclic number.

It is not a de Polignac number, because 91987971 - 2³ = 91987963 is a prime.

It is not an unprimeable number, because it can be changed into a prime (91987979) 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, 20985 + ... + 24986.

It is an arithmetic number, because the mean of its divisors is an integer number (8274960).

Almost surely, 2^91987971 is an apocalyptic number.

91987971 is a deficient number, since it is larger than the sum of its proper divisors (40411389).

91987971 is a wasteful number, since it uses less digits than its factorization.

91987971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46026.

The product of its digits is 285768, while the sum is 51.

The square root of 91987971 is about 9591.0359711556. The cubic root of 91987971 is about 451.4160676153.

The spelling of 91987971 in words is "ninety-one million, nine hundred eighty-seven thousand, nine hundred seventy-one".