21564799 has 4 divisors (see below), whose sum is σ = 21971736. Its totient is φ = 21157864.

The previous prime is 21564793. The next prime is 21564929. The reversal of 21564799 is 99746512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21564799 - 2⁷ = 21564671 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21564793) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 203389 + ... + 203494.

It is an arithmetic number, because the mean of its divisors is an integer number (5492934).

Almost surely, 2^21564799 is an apocalyptic number.

21564799 is a deficient number, since it is larger than the sum of its proper divisors (406937).

21564799 is an equidigital number, since it uses as much as digits as its factorization.

21564799 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 406936.

The product of its digits is 136080, while the sum is 43.

The square root of 21564799 is about 4643.7914466522. The cubic root of 21564799 is about 278.3439620484.

The spelling of 21564799 in words is "twenty-one million, five hundred sixty-four thousand, seven hundred ninety-nine".