21161791985 has 16 divisors (see below), whose sum is σ = 26289964800. Its totient is φ = 16333119936.

The previous prime is 21161791969. The next prime is 21161792017. The reversal of 21161791985 is 58919716112.

It is a cyclic number.

It is not a de Polignac number, because 21161791985 - 2⁴ = 21161791969 is a prime.

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, 135932 + ... + 246578.

It is an arithmetic number, because the mean of its divisors is an integer number (1643122800).

Almost surely, 2^21161791985 is an apocalyptic number.

It is an amenable number.

21161791985 is a deficient number, since it is larger than the sum of its proper divisors (5128172815).

21161791985 is a wasteful number, since it uses less digits than its factorization.

21161791985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112000.

The product of its digits is 272160, while the sum is 50.

The spelling of 21161791985 in words is "twenty-one billion, one hundred sixty-one million, seven hundred ninety-one thousand, nine hundred eighty-five".