21758365728 has 144 divisors (see below), whose sum is σ = 67698330336. Its totient is φ = 6574110720.

The previous prime is 21758365721. The next prime is 21758365757. The reversal of 21758365728 is 82756385712.

21758365728 is a `hidden beast` number, since 2 + 1 + 7 + 583 + 6 + 57 + 2 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is not an unprimeable number, because it can be changed into a prime (21758365721) 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 23 ways as a sum of consecutive naturals, for example, 1089400 + ... + 1109192.

It is an arithmetic number, because the mean of its divisors is an integer number (470127294).

Almost surely, 2^21758365728 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21758365728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33849165168).

21758365728 is an abundant number, since it is smaller than the sum of its proper divisors (45939964608).

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

21758365728 is a wasteful number, since it uses less digits than its factorization.

21758365728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20167 (or 20156 counting only the distinct ones).

The product of its digits is 5644800, while the sum is 54.

The spelling of 21758365728 in words is "twenty-one billion, seven hundred fifty-eight million, three hundred sixty-five thousand, seven hundred twenty-eight".