21404928 has 72 divisors (see below), whose sum is σ = 58278528. Its totient is φ = 6971392.

The previous prime is 21404923. The next prime is 21404941. The reversal of 21404928 is 82940412.

It is a junction number, because it is equal to n+sod(n) for n = 21404895 and 21404904.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21404923) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35800 + ... + 36392.

It is an arithmetic number, because the mean of its divisors is an integer number (809424).

Almost surely, 2^21404928 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 21404928, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29139264).

21404928 is an abundant number, since it is smaller than the sum of its proper divisors (36873600).

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

21404928 is an equidigital number, since it uses as much as digits as its factorization.

21404928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 659 (or 645 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 21404928 is about 4626.5460118754. The cubic root of 21404928 is about 277.6544193710.

The spelling of 21404928 in words is "twenty-one million, four hundred four thousand, nine hundred twenty-eight".