21728444 has 12 divisors (see below), whose sum is σ = 38648568. Its totient is φ = 10686000.

The previous prime is 21728437. The next prime is 21728467. The reversal of 21728444 is 44482712.

It is a super-2 number, since 2×21728444² = 944250557322272, which contains 22 as substring.

It is a hoax number, since the sum of its digits (32) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21728444.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 44282 + ... + 44769.

It is an arithmetic number, because the mean of its divisors is an integer number (3220714).

Almost surely, 2^21728444 is an apocalyptic number.

It is an amenable number.

21728444 is a deficient number, since it is larger than the sum of its proper divisors (16920124).

21728444 is a wasteful number, since it uses less digits than its factorization.

21728444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89116 (or 89114 counting only the distinct ones).

The product of its digits is 14336, while the sum is 32.

The square root of 21728444 is about 4661.3779078723. The cubic root of 21728444 is about 279.0462618611.

The spelling of 21728444 in words is "twenty-one million, seven hundred twenty-eight thousand, four hundred forty-four".