21665728716 has 24 divisors (see below), whose sum is σ = 51074538480. Its totient is φ = 7147456512.

The previous prime is 21665728631. The next prime is 21665728771. The reversal of 21665728716 is 61782756612.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9305421 + ... + 9307748.

It is an arithmetic number, because the mean of its divisors is an integer number (2128105770).

Almost surely, 2^21665728716 is an apocalyptic number.

It is an amenable number.

21665728716 is an abundant number, since it is smaller than the sum of its proper divisors (29408809764).

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

21665728716 is a wasteful number, since it uses less digits than its factorization.

21665728716 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18613273 (or 18613271 counting only the distinct ones).

The product of its digits is 1693440, while the sum is 51.

The spelling of 21665728716 in words is "twenty-one billion, six hundred sixty-five million, seven hundred twenty-eight thousand, seven hundred sixteen".