21865378764 has 48 divisors (see below), whose sum is σ = 51403509248. Its totient is φ = 7233686208.

The previous prime is 21865378763. The next prime is 21865378811. The reversal of 21865378764 is 46787356812.

It is not an unprimeable number, because it can be changed into a prime (21865378763) 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, 1473309 + ... + 1488075.

Almost surely, 2^21865378764 is an apocalyptic number.

It is an amenable number.

21865378764 is an abundant number, since it is smaller than the sum of its proper divisors (29538130484).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21865378764 is a wasteful number, since it uses less digits than its factorization.

21865378764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15694 (or 15692 counting only the distinct ones).

The product of its digits is 13547520, while the sum is 57.

The spelling of 21865378764 in words is "twenty-one billion, eight hundred sixty-five million, three hundred seventy-eight thousand, seven hundred sixty-four".