21243613664 has 108 divisors (see below), whose sum is σ = 52682641704. Its totient is φ = 8403962112.

The previous prime is 21243613663. The next prime is 21243613673. The reversal of 21243613664 is 46631634212.

It is a super-2 number, since 2×21243613664² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243613663) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 224909 + ... + 305075.

It is an arithmetic number, because the mean of its divisors is an integer number (487802238).

Almost surely, 2^21243613664 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 21243613664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26341320852).

21243613664 is an abundant number, since it is smaller than the sum of its proper divisors (31439028040).

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

21243613664 is a wasteful number, since it uses less digits than its factorization.

21243613664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80217 (or 80189 counting only the distinct ones).

The product of its digits is 124416, while the sum is 38.

The spelling of 21243613664 in words is "twenty-one billion, two hundred forty-three million, six hundred thirteen thousand, six hundred sixty-four".