21945440664 has 144 divisors (see below), whose sum is σ = 69199322400. Its totient is φ = 6264687744.

The previous prime is 21945440659. The next prime is 21945440687. The reversal of 21945440664 is 46604454912.

21945440664 is a `hidden beast` number, since 2 + 194 + 54 + 406 + 6 + 4 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 5886369 + ... + 5890095.

It is an arithmetic number, because the mean of its divisors is an integer number (480550850).

Almost surely, 2^21945440664 is an apocalyptic number.

21945440664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21945440664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34599661200).

21945440664 is an abundant number, since it is smaller than the sum of its proper divisors (47253881736).

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

21945440664 is a wasteful number, since it uses less digits than its factorization.

21945440664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5422 (or 5408 counting only the distinct ones).

The product of its (nonzero) digits is 829440, while the sum is 45.

The spelling of 21945440664 in words is "twenty-one billion, nine hundred forty-five million, four hundred forty thousand, six hundred sixty-four".