21728227 has 4 divisors (see below), whose sum is σ = 23006376. Its totient is φ = 20450080.

The previous prime is 21728197. The next prime is 21728233. The reversal of 21728227 is 72282712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21728227 - 2¹⁹ = 21203939 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21728297) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 639049 + ... + 639082.

It is an arithmetic number, because the mean of its divisors is an integer number (5751594).

Almost surely, 2^21728227 is an apocalyptic number.

21728227 is a deficient number, since it is larger than the sum of its proper divisors (1278149).

21728227 is a wasteful number, since it uses less digits than its factorization.

21728227 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1278148.

The product of its digits is 6272, while the sum is 31.

The square root of 21728227 is about 4661.3546314349. The cubic root of 21728227 is about 279.0453329214.

The spelling of 21728227 in words is "twenty-one million, seven hundred twenty-eight thousand, two hundred twenty-seven".