21305331664 has 20 divisors (see below), whose sum is σ = 43073823456. Its totient is φ = 10189506272.

The previous prime is 21305331631. The next prime is 21305331667. The reversal of 21305331664 is 46613350312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21305331667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28947094 + ... + 28947829.

Almost surely, 2^21305331664 is an apocalyptic number.

It is an amenable number.

21305331664 is an abundant number, since it is smaller than the sum of its proper divisors (21768491792).

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

21305331664 is a wasteful number, since it uses less digits than its factorization.

21305331664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57894954 (or 57894948 counting only the distinct ones).

The product of its (nonzero) digits is 38880, while the sum is 34.

Adding to 21305331664 its reverse (46613350312), we get a palindrome (67918681976).

The spelling of 21305331664 in words is "twenty-one billion, three hundred five million, three hundred thirty-one thousand, six hundred sixty-four".