21564646 has 4 divisors (see below), whose sum is σ = 32346972. Its totient is φ = 10782322.

The previous prime is 21564637. The next prime is 21564649. The reversal of 21564646 is 64646512.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21564649) by changing a digit.

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, 5391160 + ... + 5391163.

It is an arithmetic number, because the mean of its divisors is an integer number (8086743).

Almost surely, 2^21564646 is an apocalyptic number.

21564646 is a deficient number, since it is larger than the sum of its proper divisors (10782326).

21564646 is a wasteful number, since it uses less digits than its factorization.

21564646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10782325.

The product of its digits is 34560, while the sum is 34.

The square root of 21564646 is about 4643.7749730150. The cubic root of 21564646 is about 278.3433037731.

The spelling of 21564646 in words is "twenty-one million, five hundred sixty-four thousand, six hundred forty-six".