21564385 has 8 divisors (see below), whose sum is σ = 25975080. Its totient is φ = 17186304.

The previous prime is 21564379. The next prime is 21564391. The reversal of 21564385 is 58346512.

It is an interprime number because it is at equal distance from previous prime (21564379) and next prime (21564391).

It can be written as a sum of positive squares in 4 ways, for example, as 1957201 + 19607184 = 1399^2 + 4428^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21564385 - 2⁵ = 21564353 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21564385.

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 7 ways as a sum of consecutive naturals, for example, 6672 + ... + 9361.

It is an arithmetic number, because the mean of its divisors is an integer number (3246885).

Almost surely, 2^21564385 is an apocalyptic number.

It is an amenable number.

21564385 is a deficient number, since it is larger than the sum of its proper divisors (4410695).

21564385 is a wasteful number, since it uses less digits than its factorization.

21564385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16307.

The product of its digits is 28800, while the sum is 34.

The square root of 21564385 is about 4643.7468707930. The cubic root of 21564385 is about 278.3421808256.

The spelling of 21564385 in words is "twenty-one million, five hundred sixty-four thousand, three hundred eighty-five".