21728204 has 6 divisors (see below), whose sum is σ = 38024364. Its totient is φ = 10864100.

The previous prime is 21728197. The next prime is 21728233. The reversal of 21728204 is 40282712.

It is a super-2 number, since 2×21728204² = 944229698131232, which contains 22 as substring.

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 as a sum of consecutive naturals, namely, 2716022 + ... + 2716029.

It is an arithmetic number, because the mean of its divisors is an integer number (6337394).

Almost surely, 2^21728204 is an apocalyptic number.

It is an amenable number.

21728204 is a deficient number, since it is larger than the sum of its proper divisors (16296160).

21728204 is a wasteful number, since it uses less digits than its factorization.

21728204 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5432055 (or 5432053 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 26.

The square root of 21728204 is about 4661.3521643403. The cubic root of 21728204 is about 279.0452344620.

The spelling of 21728204 in words is "twenty-one million, seven hundred twenty-eight thousand, two hundred four".