21579728 has 10 divisors (see below), whose sum is σ = 41810754. Its totient is φ = 10789856.

The previous prime is 21579709. The next prime is 21579731. The reversal of 21579728 is 82797512.

It can be written as a sum of positive squares in only one way, i.e., 21049744 + 529984 = 4588^2 + 728^2 .

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 674351 + ... + 674382.

Almost surely, 2^21579728 is an apocalyptic number.

It is an amenable number.

21579728 is a deficient number, since it is larger than the sum of its proper divisors (20231026).

21579728 is a wasteful number, since it uses less digits than its factorization.

21579728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1348741 (or 1348735 counting only the distinct ones).

The product of its digits is 70560, while the sum is 41.

The square root of 21579728 is about 4645.3985835448. The cubic root of 21579728 is about 278.4081784051.

The spelling of 21579728 in words is "twenty-one million, five hundred seventy-nine thousand, seven hundred twenty-eight".