21023028 has 72 divisors (see below), whose sum is σ = 59241000. Its totient is φ = 6241536.

The previous prime is 21023017. The next prime is 21023047. The reversal of 21023028 is 82032012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 338724 + 20684304 = 582^2 + 4548^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a self number, because there is not a number n which added to its sum of digits gives 21023028.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 12798 + ... + 14346.

Almost surely, 2^21023028 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 21023028, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29620500).

21023028 is an abundant number, since it is smaller than the sum of its proper divisors (38217972).

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

21023028 is a wasteful number, since it uses less digits than its factorization.

21023028 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1601 (or 1596 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21023028 is about 4585.0875673208. The cubic root of 21023028 is about 275.9932260467.

The spelling of 21023028 in words is "twenty-one million, twenty-three thousand, twenty-eight".