15999318921 has 8 divisors (see below), whose sum is σ = 21333053344. Its totient is φ = 10665898560.

The previous prime is 15999318889. The next prime is 15999318983. The reversal of 15999318921 is 12981399951.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 15999318921 - 2⁵ = 15999318889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15999318421) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 95370 + ... + 202716.

It is an arithmetic number, because the mean of its divisors is an integer number (2666631668).

Almost surely, 2^15999318921 is an apocalyptic number.

It is an amenable number.

15999318921 is a deficient number, since it is larger than the sum of its proper divisors (5333734423).

15999318921 is a wasteful number, since it uses less digits than its factorization.

15999318921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157031.

The product of its digits is 1574640, while the sum is 57.

The spelling of 15999318921 in words is "fifteen billion, nine hundred ninety-nine million, three hundred eighteen thousand, nine hundred twenty-one".