21665143266 has 48 divisors (see below), whose sum is σ = 47191372416. Its totient is φ = 6627611328.

The previous prime is 21665143229. The next prime is 21665143267. The reversal of 21665143266 is 66234156612.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21665143267) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 113671 + ... + 237173.

It is an arithmetic number, because the mean of its divisors is an integer number (983153592).

Almost surely, 2^21665143266 is an apocalyptic number.

21665143266 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21665143266, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23595686208).

21665143266 is an abundant number, since it is smaller than the sum of its proper divisors (25526229150).

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

21665143266 is a wasteful number, since it uses less digits than its factorization.

21665143266 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123707 (or 123694 counting only the distinct ones).

The product of its digits is 311040, while the sum is 42.

Adding to 21665143266 its reverse (66234156612), we get a palindrome (87899299878).

The spelling of 21665143266 in words is "twenty-one billion, six hundred sixty-five million, one hundred forty-three thousand, two hundred sixty-six".