21929728 has 36 divisors (see below), whose sum is σ = 46357920. Its totient is φ = 10317824.

The previous prime is 21929723. The next prime is 21929749. The reversal of 21929728 is 82792912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21929723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1833 + ... + 6871.

It is an arithmetic number, because the mean of its divisors is an integer number (1287720).

Almost surely, 2^21929728 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 21929728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23178960).

21929728 is an abundant number, since it is smaller than the sum of its proper divisors (24428192).

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

21929728 is an equidigital number, since it uses as much as digits as its factorization.

21929728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5072 (or 5058 counting only the distinct ones).

The product of its digits is 36288, while the sum is 40.

The square root of 21929728 is about 4682.9187479605. The cubic root of 21929728 is about 279.9052740796.

The spelling of 21929728 in words is "twenty-one million, nine hundred twenty-nine thousand, seven hundred twenty-eight".