644443609 has 2 divisors, whose sum is σ = 644443610. Its totient is φ = 644443608.

The previous prime is 644443603. The next prime is 644443661. The reversal of 644443609 is 906344446.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 644144400 + 299209 = 25380^2 + 547^2 .

It is a cyclic number.

It is not a de Polignac number, because 644443609 - 2²¹ = 642346457 is a prime.

It is not a weakly prime, because it can be changed into another prime (644443603) 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, 322221804 + 322221805.

It is an arithmetic number, because the mean of its divisors is an integer number (322221805).

Almost surely, 2^644443609 is an apocalyptic number.

It is an amenable number.

644443609 is a deficient number, since it is larger than the sum of its proper divisors (1).

644443609 is an equidigital number, since it uses as much as digits as its factorization.

644443609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 248832, while the sum is 40.

The square root of 644443609 is about 25385.8938979899. The cubic root of 644443609 is about 863.7637497244.

The spelling of 644443609 in words is "six hundred forty-four million, four hundred forty-three thousand, six hundred nine".