19887478891 has 16 divisors (see below), whose sum is σ = 23065344000. Its totient is φ = 16795171008.

The previous prime is 19887478879. The next prime is 19887478907.

19887478891 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 19887478891 - 2²¹ = 19885381739 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 19887478891.

It is not an unprimeable number, because it can be changed into a prime (19887478591) 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, 119910 + ... + 232708.

It is an arithmetic number, because the mean of its divisors is an integer number (1441584000).

Almost surely, 2^19887478891 is an apocalyptic number.

19887478891 is a deficient number, since it is larger than the sum of its proper divisors (3177865109).

19887478891 is a wasteful number, since it uses less digits than its factorization.

19887478891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 113178.

The product of its digits is 65028096, while the sum is 70.

The spelling of 19887478891 in words is "nineteen billion, eight hundred eighty-seven million, four hundred seventy-eight thousand, eight hundred ninety-one".