21644646 has 16 divisors (see below), whose sum is σ = 43883184. Its totient is φ = 7115904.

The previous prime is 21644641. The next prime is 21644653. The reversal of 21644646 is 64644612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21644641) 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 in 7 ways as a sum of consecutive naturals, for example, 24271 + ... + 25146.

It is an arithmetic number, because the mean of its divisors is an integer number (2742699).

Almost surely, 2^21644646 is an apocalyptic number.

21644646 is an abundant number, since it is smaller than the sum of its proper divisors (22238538).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21644646 is a wasteful number, since it uses less digits than its factorization.

21644646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49495.

The product of its digits is 27648, while the sum is 33.

The square root of 21644646 is about 4652.3806808988. The cubic root of 21644646 is about 278.6870760929.

The spelling of 21644646 in words is "twenty-one million, six hundred forty-four thousand, six hundred forty-six".