21665386644 has 48 divisors (see below), whose sum is σ = 55327996416. Its totient is φ = 6543871200.

The previous prime is 21665386627. The next prime is 21665386651. The reversal of 21665386644 is 44668356612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 226792 + ... + 307839.

It is an arithmetic number, because the mean of its divisors is an integer number (1152666592).

Almost surely, 2^21665386644 is an apocalyptic number.

It is an amenable number.

21665386644 is an abundant number, since it is smaller than the sum of its proper divisors (33662609772).

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

21665386644 is a wasteful number, since it uses less digits than its factorization.

21665386644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 534956 (or 534954 counting only the distinct ones).

The product of its digits is 4976640, while the sum is 51.

The spelling of 21665386644 in words is "twenty-one billion, six hundred sixty-five million, three hundred eighty-six thousand, six hundred forty-four".