21605572 has 12 divisors (see below), whose sum is σ = 40033980. Its totient is φ = 10167296.

The previous prime is 21605569. The next prime is 21605587. The reversal of 21605572 is 27550612.

It can be written as a sum of positive squares in 2 ways, for example, as 14561856 + 7043716 = 3816^2 + 2654^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21605572.

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 in 3 ways as a sum of consecutive naturals, for example, 158797 + ... + 158932.

It is an arithmetic number, because the mean of its divisors is an integer number (3336165).

Almost surely, 2^21605572 is an apocalyptic number.

It is an amenable number.

21605572 is a deficient number, since it is larger than the sum of its proper divisors (18428408).

21605572 is a wasteful number, since it uses less digits than its factorization.

21605572 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 317750 (or 317748 counting only the distinct ones).

The product of its (nonzero) digits is 4200, while the sum is 28.

The square root of 21605572 is about 4648.1794285505. The cubic root of 21605572 is about 278.5192751181.

The spelling of 21605572 in words is "twenty-one million, six hundred five thousand, five hundred seventy-two".