21644243233 has 2 divisors, whose sum is σ = 21644243234. Its totient is φ = 21644243232.

The previous prime is 21644243207. The next prime is 21644243237. The reversal of 21644243233 is 33234244612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20768556769 + 875686464 = 144113^2 + 29592^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21644243233 is a prime.

It is not a weakly prime, because it can be changed into another prime (21644243237) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10822121616 + 10822121617.

It is an arithmetic number, because the mean of its divisors is an integer number (10822121617).

Almost surely, 2^21644243233 is an apocalyptic number.

It is an amenable number.

21644243233 is a deficient number, since it is larger than the sum of its proper divisors (1).

21644243233 is an equidigital number, since it uses as much as digits as its factorization.

21644243233 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 82944, while the sum is 34.

Adding to 21644243233 its reverse (33234244612), we get a palindrome (54878487845).

The spelling of 21644243233 in words is "twenty-one billion, six hundred forty-four million, two hundred forty-three thousand, two hundred thirty-three".