21540644 has 12 divisors (see below), whose sum is σ = 37728768. Its totient is φ = 10761000.

The previous prime is 21540637. The next prime is 21540653. The reversal of 21540644 is 44604512.

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, 7169 + ... + 9719.

It is an arithmetic number, because the mean of its divisors is an integer number (3144064).

Almost surely, 2^21540644 is an apocalyptic number.

It is an amenable number.

21540644 is a deficient number, since it is larger than the sum of its proper divisors (16188124).

21540644 is a wasteful number, since it uses less digits than its factorization.

21540644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4666 (or 4664 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 26.

The square root of 21540644 is about 4641.1899336269. The cubic root of 21540644 is about 278.2399977084.

The spelling of 21540644 in words is "twenty-one million, five hundred forty thousand, six hundred forty-four".