21644046021 has 16 divisors (see below), whose sum is σ = 31542494144. Its totient is φ = 13120614144.

The previous prime is 21644045989. The next prime is 21644046059. The reversal of 21644046021 is 12064044612.

It is a happy number.

It is not a de Polignac number, because 21644046021 - 2⁵ = 21644045989 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21644046021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21644036021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4138996 + ... + 4144221.

It is an arithmetic number, because the mean of its divisors is an integer number (1971405884).

Almost surely, 2^21644046021 is an apocalyptic number.

It is an amenable number.

21644046021 is a deficient number, since it is larger than the sum of its proper divisors (9898448123).

21644046021 is a wasteful number, since it uses less digits than its factorization.

21644046021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8283300.

The product of its (nonzero) digits is 9216, while the sum is 30.

The spelling of 21644046021 in words is "twenty-one billion, six hundred forty-four million, forty-six thousand, twenty-one".