21644045989 has 2 divisors, whose sum is σ = 21644045990. Its totient is φ = 21644045988.

The previous prime is 21644045963. The next prime is 21644046059. The reversal of 21644045989 is 98954044612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17682350625 + 3961695364 = 132975^2 + 62942^2 .

It is a cyclic number.

It is not a de Polignac number, because 21644045989 - 2⁵ = 21644045957 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21644045939) 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 as a sum of consecutive naturals, namely, 10822022994 + 10822022995.

It is an arithmetic number, because the mean of its divisors is an integer number (10822022995).

Almost surely, 2^21644045989 is an apocalyptic number.

It is an amenable number.

21644045989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21644045989 is an equidigital number, since it uses as much as digits as its factorization.

21644045989 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2488320, while the sum is 52.

The spelling of 21644045989 in words is "twenty-one billion, six hundred forty-four million, forty-five thousand, nine hundred eighty-nine".