21197578785 has 16 divisors (see below), whose sum is σ = 34001566656. Its totient is φ = 11276895168.

The previous prime is 21197578769. The next prime is 21197578811. The reversal of 21197578785 is 58787579112.

It is not a de Polignac number, because 21197578785 - 2⁴ = 21197578769 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, 1773859 + ... + 1785768.

It is an arithmetic number, because the mean of its divisors is an integer number (2125097916).

Almost surely, 2^21197578785 is an apocalyptic number.

It is an amenable number.

21197578785 is a deficient number, since it is larger than the sum of its proper divisors (12803987871).

21197578785 is a wasteful number, since it uses less digits than its factorization.

21197578785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3560032.

The product of its digits is 9878400, while the sum is 60.

The spelling of 21197578785 in words is "twenty-one billion, one hundred ninety-seven million, five hundred seventy-eight thousand, seven hundred eighty-five".