79990721 has 2 divisors, whose sum is σ = 79990722. Its totient is φ = 79990720.

The previous prime is 79990717. The next prime is 79990723. The reversal of 79990721 is 12709997.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 54184321 + 25806400 = 7361^2 + 5080^2 .

It is an emirp because it is prime and its reverse (12709997) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 79990721 - 2² = 79990717 is a prime.

It is a Sophie Germain prime.

Together with 79990723, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (79990723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39995360 + 39995361.

It is an arithmetic number, because the mean of its divisors is an integer number (39995361).

Almost surely, 2^79990721 is an apocalyptic number.

It is an amenable number.

79990721 is a deficient number, since it is larger than the sum of its proper divisors (1).

79990721 is an equidigital number, since it uses as much as digits as its factorization.

79990721 is an evil number, because the sum of its binary digits is even.

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

The square root of 79990721 is about 8943.7531830882. The cubic root of 79990721 is about 430.8702781960.

The spelling of 79990721 in words is "seventy-nine million, nine hundred ninety thousand, seven hundred twenty-one".