79721891 has 8 divisors (see below), whose sum is σ = 88854480. Its totient is φ = 71083008.

The previous prime is 79721881. The next prime is 79721903. The reversal of 79721891 is 19812797.

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 79721891 - 2⁶ = 79721827 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (79721881) 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, 123086 + ... + 123731.

It is an arithmetic number, because the mean of its divisors is an integer number (11106810).

Almost surely, 2^79721891 is an apocalyptic number.

79721891 is a deficient number, since it is larger than the sum of its proper divisors (9132589).

79721891 is a wasteful number, since it uses less digits than its factorization.

79721891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 246853.

The product of its digits is 63504, while the sum is 44.

The square root of 79721891 is about 8928.7116091853. The cubic root of 79721891 is about 430.3870518987.

The spelling of 79721891 in words is "seventy-nine million, seven hundred twenty-one thousand, eight hundred ninety-one".