21650728 has 64 divisors (see below), whose sum is σ = 48729600. Its totient is φ = 8902080.

The previous prime is 21650719. The next prime is 21650731. The reversal of 21650728 is 82705612.

It is a self number, because there is not a number n which added to its sum of digits gives 21650728.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 38175 + ... + 38737.

It is an arithmetic number, because the mean of its divisors is an integer number (761400).

Almost surely, 2^21650728 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 21650728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24364800).

21650728 is an abundant number, since it is smaller than the sum of its proper divisors (27078872).

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

21650728 is a wasteful number, since it uses less digits than its factorization.

21650728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 622 (or 618 counting only the distinct ones).

The product of its (nonzero) digits is 6720, while the sum is 31.

The square root of 21650728 is about 4653.0342788335. The cubic root of 21650728 is about 278.7131767133.

The spelling of 21650728 in words is "twenty-one million, six hundred fifty thousand, seven hundred twenty-eight".