21529728 has 96 divisors (see below), whose sum is σ = 67626000. Its totient is φ = 6520320.

The previous prime is 21529709. The next prime is 21529733. The reversal of 21529728 is 82792512.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21529692 and 21529701.

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, 11823 + ... + 13521.

Almost surely, 2^21529728 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 21529728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33813000).

21529728 is an abundant number, since it is smaller than the sum of its proper divisors (46096272).

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

21529728 is a wasteful number, since it uses less digits than its factorization.

21529728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1730 (or 1715 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 21529728 is about 4640.0137930829. The cubic root of 21529728 is about 278.1929891941.

The spelling of 21529728 in words is "twenty-one million, five hundred twenty-nine thousand, seven hundred twenty-eight".