91665621 has 16 divisors (see below), whose sum is σ = 137051200. Its totient is φ = 60547824.

The previous prime is 91665619. The next prime is 91665641. The reversal of 91665621 is 12656619.

91665621 is a `hidden beast` number, since 91 + 6 + 6 + 562 + 1 = 666.

It is not a de Polignac number, because 91665621 - 2¹ = 91665619 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91665601) 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, 12631 + ... + 18516.

It is an arithmetic number, because the mean of its divisors is an integer number (8565700).

Almost surely, 2^91665621 is an apocalyptic number.

It is an amenable number.

91665621 is a deficient number, since it is larger than the sum of its proper divisors (45385579).

91665621 is a wasteful number, since it uses less digits than its factorization.

91665621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31265 (or 31259 counting only the distinct ones).

The product of its digits is 19440, while the sum is 36.

The square root of 91665621 is about 9574.2164692470. The cubic root of 91665621 is about 450.8881570181. Note that the first 3 decimals are identical.

The spelling of 91665621 in words is "ninety-one million, six hundred sixty-five thousand, six hundred twenty-one".