19887915805 has 16 divisors (see below), whose sum is σ = 24083118000. Its totient is φ = 15765765120.

The previous prime is 19887915791. The next prime is 19887915857. The reversal of 19887915805 is 50851978891.

It can be written as a sum of positive squares in 8 ways, for example, as 12348987876 + 7538927929 = 111126^2 + 86827^2 .

It is a de Polignac number, because none of the positive numbers 2^k-19887915805 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 281941 + ... + 345349.

It is an arithmetic number, because the mean of its divisors is an integer number (1505194875).

Almost surely, 2^19887915805 is an apocalyptic number.

It is an amenable number.

19887915805 is a deficient number, since it is larger than the sum of its proper divisors (4195202195).

19887915805 is a wasteful number, since it uses less digits than its factorization.

19887915805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63984.

The product of its (nonzero) digits is 7257600, while the sum is 61.

The spelling of 19887915805 in words is "nineteen billion, eight hundred eighty-seven million, nine hundred fifteen thousand, eight hundred five".