21306991392 has 72 divisors (see below), whose sum is σ = 60644460240. Its totient is φ = 7096152960.

The previous prime is 21306991379. The next prime is 21306991493. The reversal of 21306991392 is 29319960312.

It is a tau number, because it is divible by the number of its divisors (72).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 305659 + ... + 368837.

It is an arithmetic number, because the mean of its divisors is an integer number (842284170).

Almost surely, 2^21306991392 is an apocalyptic number.

It is an amenable number.

21306991392 is an abundant number, since it is smaller than the sum of its proper divisors (39337468848).

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

21306991392 is a wasteful number, since it uses less digits than its factorization.

21306991392 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64366 (or 64355 counting only the distinct ones).

The product of its (nonzero) digits is 157464, while the sum is 45.

The spelling of 21306991392 in words is "twenty-one billion, three hundred six million, nine hundred ninety-one thousand, three hundred ninety-two".