15997970721 has 16 divisors (see below), whose sum is σ = 22457661440. Its totient is φ = 10102015440.

The previous prime is 15997970623. The next prime is 15997970743. The reversal of 15997970721 is 12707979951.

15997970721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 15997970721 - 2¹³ = 15997962529 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (57).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15997920721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 302916 + ... + 351786.

It is an arithmetic number, because the mean of its divisors is an integer number (1403603840).

Almost surely, 2^15997970721 is an apocalyptic number.

It is an amenable number.

15997970721 is a deficient number, since it is larger than the sum of its proper divisors (6459690719).

15997970721 is a wasteful number, since it uses less digits than its factorization.

15997970721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54636.

The product of its (nonzero) digits is 2500470, while the sum is 57.

The spelling of 15997970721 in words is "fifteen billion, nine hundred ninety-seven million, nine hundred seventy thousand, seven hundred twenty-one".