79902721 has 4 divisors (see below), whose sum is σ = 82062292. Its totient is φ = 77743152.

The previous prime is 79902709. The next prime is 79902731. The reversal of 79902721 is 12720997.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 70224400 + 9678321 = 8380^2 + 3111^2 .

It is a cyclic number.

It is not a de Polignac number, because 79902721 - 2¹⁹ = 79378433 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37), and also a Moran number because the ratio is a prime number: 2159533 = 79902721 / (7 + 9 + 9 + 0 + 2 + 7 + 2 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (79902731) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1079730 + ... + 1079803.

It is an arithmetic number, because the mean of its divisors is an integer number (20515573).

Almost surely, 2^79902721 is an apocalyptic number.

It is an amenable number.

79902721 is a deficient number, since it is larger than the sum of its proper divisors (2159571).

79902721 is a wasteful number, since it uses less digits than its factorization.

79902721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2159570.

The product of its (nonzero) digits is 15876, while the sum is 37.

The square root of 79902721 is about 8938.8321944200. The cubic root of 79902721 is about 430.7122161238.

The spelling of 79902721 in words is "seventy-nine million, nine hundred two thousand, seven hundred twenty-one".