21864789666 has 96 divisors (see below), whose sum is σ = 51232662000. Its totient is φ = 6714470400.

The previous prime is 21864789641. The next prime is 21864789697. The reversal of 21864789666 is 66698746812.

It can be written as a sum of positive squares in 8 ways, for example, as 16442676441 + 5422113225 = 128229^2 + 73635^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2746660 + ... + 2754608.

Almost surely, 2^21864789666 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21864789666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25616331000).

21864789666 is an abundant number, since it is smaller than the sum of its proper divisors (29367872334).

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

21864789666 is a wasteful number, since it uses less digits than its factorization.

21864789666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8164 (or 8161 counting only the distinct ones).

The product of its digits is 41803776, while the sum is 63.

The spelling of 21864789666 in words is "twenty-one billion, eight hundred sixty-four million, seven hundred eighty-nine thousand, six hundred sixty-six".