21928764 has 72 divisors (see below), whose sum is σ = 60504192. Its totient is φ = 6127680.

The previous prime is 21928763. The next prime is 21928769. The reversal of 21928764 is 46782912.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21928763) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 21817 + ... + 22799.

It is an arithmetic number, because the mean of its divisors is an integer number (840336).

Almost surely, 2^21928764 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21928764, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30252096).

21928764 is an abundant number, since it is smaller than the sum of its proper divisors (38575428).

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

21928764 is a wasteful number, since it uses less digits than its factorization.

21928764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1027 (or 1012 counting only the distinct ones).

The product of its digits is 48384, while the sum is 39.

The square root of 21928764 is about 4682.8158195684. The cubic root of 21928764 is about 279.9011726055.

The spelling of 21928764 in words is "twenty-one million, nine hundred twenty-eight thousand, seven hundred sixty-four".