91517721 has 16 divisors (see below), whose sum is σ = 123871680. Its totient is φ = 60093440.

The previous prime is 91517693. The next prime is 91517731. The reversal of 91517721 is 12771519.

It is a cyclic number.

It is not a de Polignac number, because 91517721 - 2²² = 87323417 is a prime.

It is not an unprimeable number, because it can be changed into a prime (91517731) 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, 93766 + ... + 94736.

It is an arithmetic number, because the mean of its divisors is an integer number (7741980).

Almost surely, 2^91517721 is an apocalyptic number.

It is an amenable number.

91517721 is a deficient number, since it is larger than the sum of its proper divisors (32353959).

91517721 is a wasteful number, since it uses less digits than its factorization.

91517721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1416.

The product of its digits is 4410, while the sum is 33.

The square root of 91517721 is about 9566.4894815183. The cubic root of 91517721 is about 450.6455278644.

The spelling of 91517721 in words is "ninety-one million, five hundred seventeen thousand, seven hundred twenty-one".