21728534 has 16 divisors (see below), whose sum is σ = 33121440. Its totient is φ = 10689600.

The previous prime is 21728527. The next prime is 21728563. The reversal of 21728534 is 43582712.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21728534.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 52922 + ... + 53330.

It is an arithmetic number, because the mean of its divisors is an integer number (2070090).

Almost surely, 2^21728534 is an apocalyptic number.

21728534 is a deficient number, since it is larger than the sum of its proper divisors (11392906).

21728534 is a wasteful number, since it uses less digits than its factorization.

21728534 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 775.

The product of its digits is 13440, while the sum is 32.

The square root of 21728534 is about 4661.3875616602. The cubic root of 21728534 is about 279.0466471338.

The spelling of 21728534 in words is "twenty-one million, seven hundred twenty-eight thousand, five hundred thirty-four".