21728863 has 4 divisors (see below), whose sum is σ = 23400328. Its totient is φ = 20057400.

The previous prime is 21728857. The next prime is 21728867. The reversal of 21728863 is 36882712.

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 21728863 - 2⁵ = 21728831 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21728867) 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, 835713 + ... + 835738.

It is an arithmetic number, because the mean of its divisors is an integer number (5850082).

Almost surely, 2^21728863 is an apocalyptic number.

21728863 is a deficient number, since it is larger than the sum of its proper divisors (1671465).

21728863 is a wasteful number, since it uses less digits than its factorization.

21728863 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1671464.

The product of its digits is 32256, while the sum is 37.

The square root of 21728863 is about 4661.4228514478. The cubic root of 21728863 is about 279.0480555105.

The spelling of 21728863 in words is "twenty-one million, seven hundred twenty-eight thousand, eight hundred sixty-three".