15720808721 has 4 divisors (see below), whose sum is σ = 15882879012. Its totient is φ = 15558738432.

The previous prime is 15720808717. The next prime is 15720808739. The reversal of 15720808721 is 12780802751.

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 10559823121 + 5160985600 = 102761^2 + 71840^2 .

It is a cyclic number.

It is not a de Polignac number, because 15720808721 - 2² = 15720808717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15720808781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 81035000 + ... + 81035193.

It is an arithmetic number, because the mean of its divisors is an integer number (3970719753).

Almost surely, 2^15720808721 is an apocalyptic number.

It is an amenable number.

15720808721 is a deficient number, since it is larger than the sum of its proper divisors (162070291).

15720808721 is an equidigital number, since it uses as much as digits as its factorization.

15720808721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 162070290.

The product of its (nonzero) digits is 62720, while the sum is 41.

The spelling of 15720808721 in words is "fifteen billion, seven hundred twenty million, eight hundred eight thousand, seven hundred twenty-one".