19999999999891 has 4 divisors (see below), whose sum is σ = 20000291320800. Its totient is φ = 19999708678984.

The previous prime is 19999999999871. The next prime is 19999999999907. The reversal of 19999999999891 is 19899999999991.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19999999999891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19999999999831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 145557451 + ... + 145694788.

It is an arithmetic number, because the mean of its divisors is an integer number (5000072830200).

Almost surely, 2^{19999999999891} is an apocalyptic number.

19999999999891 is a deficient number, since it is larger than the sum of its proper divisors (291320909).

19999999999891 is an equidigital number, since it uses as much as digits as its factorization.

19999999999891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291320908.

The product of its digits is 251048476872, while the sum is 109.

The spelling of 19999999999891 in words is "nineteen trillion, nine hundred ninety-nine billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, eight hundred ninety-one".