21643356689 has 2 divisors, whose sum is σ = 21643356690. Its totient is φ = 21643356688.

The previous prime is 21643356673. The next prime is 21643356737. The reversal of 21643356689 is 98665334612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21592833025 + 50523664 = 146945^2 + 7108^2 .

It is a cyclic number.

It is not a de Polignac number, because 21643356689 - 2⁴ = 21643356673 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21643356689.

It is not a weakly prime, because it can be changed into another prime (21643356389) 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, 10821678344 + 10821678345.

It is an arithmetic number, because the mean of its divisors is an integer number (10821678345).

Almost surely, 2^21643356689 is an apocalyptic number.

It is an amenable number.

21643356689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21643356689 is an equidigital number, since it uses as much as digits as its factorization.

21643356689 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5598720, while the sum is 53.

The spelling of 21643356689 in words is "twenty-one billion, six hundred forty-three million, three hundred fifty-six thousand, six hundred eighty-nine".