21538839564 has 72 divisors (see below), whose sum is σ = 59454721872. Its totient is φ = 6520356480.

The previous prime is 21538839551. The next prime is 21538839583. The reversal of 21538839564 is 46593883512.

21538839564 is a `hidden beast` number, since 2 + 15 + 38 + 8 + 39 + 564 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 21538839564.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 374302 + ... + 427994.

It is an arithmetic number, because the mean of its divisors is an integer number (825760026).

Almost surely, 2^21538839564 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 21538839564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29727360936).

21538839564 is an abundant number, since it is smaller than the sum of its proper divisors (37915882308).

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

21538839564 is a wasteful number, since it uses less digits than its factorization.

21538839564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54727 (or 54722 counting only the distinct ones).

The product of its digits is 6220800, while the sum is 54.

The spelling of 21538839564 in words is "twenty-one billion, five hundred thirty-eight million, eight hundred thirty-nine thousand, five hundred sixty-four".