21866609664 has 132 divisors (see below), whose sum is σ = 65478600824. Its totient is φ = 7288786944.

The previous prime is 21866609659. The next prime is 21866609693. The reversal of 21866609664 is 46690666812.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a self number, because there is not a number n which added to its sum of digits gives 21866609664.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 204894 + ... + 292770.

Almost surely, 2^21866609664 is an apocalyptic number.

21866609664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21866609664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32739300412).

21866609664 is an abundant number, since it is smaller than the sum of its proper divisors (43611991160).

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

21866609664 is an frugal number, since it uses more digits than its factorization.

21866609664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87912 (or 87882 counting only the distinct ones).

The product of its (nonzero) digits is 4478976, while the sum is 54.

It can be divided in two parts, 2186660 and 9664, that added together give a square (2196324 = 1482²).

The spelling of 21866609664 in words is "twenty-one billion, eight hundred sixty-six million, six hundred nine thousand, six hundred sixty-four".