91661931 has 6 divisors (see below), whose sum is σ = 132400580. Its totient is φ = 61107948.

The previous prime is 91661929. The next prime is 91661957. The reversal of 91661931 is 13916619.

91661931 is a `hidden beast` number, since 9 + 1 + 6 + 619 + 31 = 666.

It is not a de Polignac number, because 91661931 - 2¹ = 91661929 is a prime.

It is a super-2 number, since 2×91661931² = 16803819189297522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91661971) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5092321 + ... + 5092338.

Almost surely, 2^91661931 is an apocalyptic number.

91661931 is a deficient number, since it is larger than the sum of its proper divisors (40738649).

91661931 is a wasteful number, since it uses less digits than its factorization.

91661931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10184665 (or 10184662 counting only the distinct ones).

The product of its digits is 8748, while the sum is 36.

The square root of 91661931 is about 9574.0237622433. The cubic root of 91661931 is about 450.8821067686.

The spelling of 91661931 in words is "ninety-one million, six hundred sixty-one thousand, nine hundred thirty-one".