21644243263 has 4 divisors (see below), whose sum is σ = 21687619000. Its totient is φ = 21600867528.

The previous prime is 21644243237. The next prime is 21644243329. The reversal of 21644243263 is 36234244612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21644243263 - 2⁹ = 21644242751 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21644243233) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21687120 + ... + 21688117.

It is an arithmetic number, because the mean of its divisors is an integer number (5421904750).

Almost surely, 2^21644243263 is an apocalyptic number.

21644243263 is a deficient number, since it is larger than the sum of its proper divisors (43375737).

21644243263 is an equidigital number, since it uses as much as digits as its factorization.

21644243263 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43375736.

The product of its digits is 165888, while the sum is 37.

Adding to 21644243263 its reverse (36234244612), we get a palindrome (57878487875).

The spelling of 21644243263 in words is "twenty-one billion, six hundred forty-four million, two hundred forty-three thousand, two hundred sixty-three".