19788991851 has 16 divisors (see below), whose sum is σ = 26493161760. Its totient is φ = 13138836480.

The previous prime is 19788991799. The next prime is 19788991867. The reversal of 19788991851 is 15819988791.

It is not a de Polignac number, because 19788991851 - 2¹⁵ = 19788959083 is a prime.

It is not an unprimeable number, because it can be changed into a prime (19788991051) 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, 866641 + ... + 889181.

It is an arithmetic number, because the mean of its divisors is an integer number (1655822610).

Almost surely, 2^19788991851 is an apocalyptic number.

19788991851 is a deficient number, since it is larger than the sum of its proper divisors (6704169909).

19788991851 is a wasteful number, since it uses less digits than its factorization.

19788991851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23726.

The product of its digits is 13063680, while the sum is 66.

The spelling of 19788991851 in words is "nineteen billion, seven hundred eighty-eight million, nine hundred ninety-one thousand, eight hundred fifty-one".