79721917 has 16 divisors (see below), whose sum is σ = 91010304. Its totient is φ = 69184000.

The previous prime is 79721903. The next prime is 79721923. The reversal of 79721917 is 71912797.

It is a de Polignac number, because none of the positive numbers 2^k-79721917 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (79721927) 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, 19317 + ... + 23077.

It is an arithmetic number, because the mean of its divisors is an integer number (5688144).

Almost surely, 2^79721917 is an apocalyptic number.

It is an amenable number.

79721917 is a deficient number, since it is larger than the sum of its proper divisors (11288387).

79721917 is a wasteful number, since it uses less digits than its factorization.

79721917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3860.

The product of its digits is 55566, while the sum is 43.

The square root of 79721917 is about 8928.7130651623. The cubic root of 79721917 is about 430.3870986866.

It can be divided in two parts, 7972 and 1917, that added together give a palindrome (9889).

The spelling of 79721917 in words is "seventy-nine million, seven hundred twenty-one thousand, nine hundred seventeen".