15987972221 has 16 divisors (see below), whose sum is σ = 17978983680. Its totient is φ = 14106597120.

The previous prime is 15987972211. The next prime is 15987972241. The reversal of 15987972221 is 12227978951.

It is a cyclic number.

It is not a de Polignac number, because 15987972221 - 2⁶ = 15987972157 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15987972211) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 427256 + ... + 463166.

It is an arithmetic number, because the mean of its divisors is an integer number (1123686480).

Almost surely, 2^15987972221 is an apocalyptic number.

It is an amenable number.

15987972221 is a deficient number, since it is larger than the sum of its proper divisors (1991011459).

15987972221 is a wasteful number, since it uses less digits than its factorization.

15987972221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37436.

The product of its digits is 1270080, while the sum is 53.

The spelling of 15987972221 in words is "fifteen billion, nine hundred eighty-seven million, nine hundred seventy-two thousand, two hundred twenty-one".