91656721 has 8 divisors (see below), whose sum is σ = 100808064. Its totient is φ = 82805520.

The previous prime is 91656701. The next prime is 91656731. The reversal of 91656721 is 12765619.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 91656721 - 2¹⁵ = 91623953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91656701) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 74395 + ... + 75616.

It is an arithmetic number, because the mean of its divisors is an integer number (12601008).

Almost surely, 2^91656721 is an apocalyptic number.

It is an amenable number.

91656721 is a deficient number, since it is larger than the sum of its proper divisors (9151343).

91656721 is a wasteful number, since it uses less digits than its factorization.

91656721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150071.

The product of its digits is 22680, while the sum is 37.

The square root of 91656721 is about 9573.7516679722. The cubic root of 91656721 is about 450.8735639990.

The spelling of 91656721 in words is "ninety-one million, six hundred fifty-six thousand, seven hundred twenty-one".