91981881 has 12 divisors (see below), whose sum is σ = 137444580. Its totient is φ = 59206560.

The previous prime is 91981829. The next prime is 91981913. The reversal of 91981881 is 18818919.

It can be written as a sum of positive squares in 2 ways, for example, as 67568400 + 24413481 = 8220^2 + 4941^2 .

It is not a de Polignac number, because 91981881 - 2⁷ = 91981753 is a prime.

It is a super-2 number, since 2×91981881² = 16921332864596322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (91981481) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 175950 + ... + 176471.

It is an arithmetic number, because the mean of its divisors is an integer number (11453715).

Almost surely, 2^91981881 is an apocalyptic number.

It is an amenable number.

91981881 is a deficient number, since it is larger than the sum of its proper divisors (45462699).

91981881 is a wasteful number, since it uses less digits than its factorization.

91981881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 352456 (or 352453 counting only the distinct ones).

The product of its digits is 41472, while the sum is 45.

The square root of 91981881 is about 9590.7184819491. The cubic root of 91981881 is about 451.4061054993.

The spelling of 91981881 in words is "ninety-one million, nine hundred eighty-one thousand, eight hundred eighty-one".