21728524 has 12 divisors (see below), whose sum is σ = 38952648. Its totient is φ = 10599200.

The previous prime is 21728513. The next prime is 21728527. The reversal of 21728524 is 42582712.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21728527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66082 + ... + 66409.

It is an arithmetic number, because the mean of its divisors is an integer number (3246054).

Almost surely, 2^21728524 is an apocalyptic number.

It is an amenable number.

21728524 is a deficient number, since it is larger than the sum of its proper divisors (17224124).

21728524 is a wasteful number, since it uses less digits than its factorization.

21728524 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132536 (or 132534 counting only the distinct ones).

The product of its digits is 8960, while the sum is 31.

The square root of 21728524 is about 4661.3864890180. The cubic root of 21728524 is about 279.0466043258.

The spelling of 21728524 in words is "twenty-one million, seven hundred twenty-eight thousand, five hundred twenty-four".