20016979891 has 4 divisors (see below), whose sum is σ = 20017412800. Its totient is φ = 20016546984.

The previous prime is 20016979889. The next prime is 20016979897. The reversal of 20016979891 is 19897961002.

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

It is a cyclic number.

It is not a de Polignac number, because 20016979891 - 2¹ = 20016979889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20016979897) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 137496 + ... + 242773.

It is an arithmetic number, because the mean of its divisors is an integer number (5004353200).

Almost surely, 2^20016979891 is an apocalyptic number.

20016979891 is a deficient number, since it is larger than the sum of its proper divisors (432909).

20016979891 is an equidigital number, since it uses as much as digits as its factorization.

20016979891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 432908.

The product of its (nonzero) digits is 489888, while the sum is 52.

The spelling of 20016979891 in words is "twenty billion, sixteen million, nine hundred seventy-nine thousand, eight hundred ninety-one".