21305105664 has 72 divisors (see below), whose sum is σ = 58657976160. Its totient is φ = 6856808448.

The previous prime is 21305105641. The next prime is 21305105683. The reversal of 21305105664 is 46650150312.

It is a congruent number.

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, 456022 + ... + 500565.

Almost surely, 2^21305105664 is an apocalyptic number.

21305105664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21305105664 is an abundant number, since it is smaller than the sum of its proper divisors (37352870496).

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

21305105664 is an equidigital number, since it uses as much as digits as its factorization.

21305105664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 956635 (or 956621 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 33.

Adding to 21305105664 its reverse (46650150312), we get a palindrome (67955255976).

The spelling of 21305105664 in words is "twenty-one billion, three hundred five million, one hundred five thousand, six hundred sixty-four".