79909721 has 4 divisors (see below), whose sum is σ = 79928244. Its totient is φ = 79891200.

The previous prime is 79909699. The next prime is 79909727. The reversal of 79909721 is 12790997.

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 50965321 + 28944400 = 7139^2 + 5380^2 .

It is a cyclic number.

It is not a de Polignac number, because 79909721 - 2¹⁴ = 79893337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (79909727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1001 + ... + 12681.

It is an arithmetic number, because the mean of its divisors is an integer number (19982061).

Almost surely, 2^79909721 is an apocalyptic number.

It is an amenable number.

79909721 is a deficient number, since it is larger than the sum of its proper divisors (18523).

79909721 is a wasteful number, since it uses less digits than its factorization.

79909721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18522.

The product of its (nonzero) digits is 71442, while the sum is 44.

The square root of 79909721 is about 8939.2237358733. The cubic root of 79909721 is about 430.7247934906.

The spelling of 79909721 in words is "seventy-nine million, nine hundred nine thousand, seven hundred twenty-one".