21778564768 has 48 divisors (see below), whose sum is σ = 44411409000. Its totient is φ = 10500431872.

The previous prime is 21778564763. The next prime is 21778564853. The reversal of 21778564768 is 86746587712.

It can be written as a sum of positive squares in 4 ways, for example, as 18816157584 + 2962407184 = 137172^2 + 54428^2 .

It is not an unprimeable number, because it can be changed into a prime (21778564763) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 736248 + ... + 765256.

Almost surely, 2^21778564768 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 21778564768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22205704500).

21778564768 is an abundant number, since it is smaller than the sum of its proper divisors (22632844232).

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

21778564768 is a wasteful number, since it uses less digits than its factorization.

21778564768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29857 (or 29849 counting only the distinct ones).

The product of its digits is 31610880, while the sum is 61.

The spelling of 21778564768 in words is "twenty-one billion, seven hundred seventy-eight million, five hundred sixty-four thousand, seven hundred sixty-eight".