21320386728 has 64 divisors (see below), whose sum is σ = 55636329600. Its totient is φ = 6795613440.

The previous prime is 21320386673. The next prime is 21320386729. The reversal of 21320386728 is 82768302312.

It is a self number, because there is not a number n which added to its sum of digits gives 21320386728.

It is not an unprimeable number, because it can be changed into a prime (21320386729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3236398 + ... + 3242978.

It is an arithmetic number, because the mean of its divisors is an integer number (869317650).

Almost surely, 2^21320386728 is an apocalyptic number.

It is an amenable number.

21320386728 is an abundant number, since it is smaller than the sum of its proper divisors (34315942872).

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

21320386728 is a wasteful number, since it uses less digits than its factorization.

21320386728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12482 (or 12478 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 42.

The spelling of 21320386728 in words is "twenty-one billion, three hundred twenty million, three hundred eighty-six thousand, seven hundred twenty-eight".