644352209 has 2 divisors, whose sum is σ = 644352210. Its totient is φ = 644352208.

The previous prime is 644352197. The next prime is 644352223. The reversal of 644352209 is 902253446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 469372225 + 174979984 = 21665^2 + 13228^2 .

It is a cyclic number.

It is not a de Polignac number, because 644352209 - 2²⁸ = 375916753 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (644352259) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322176104 + 322176105.

It is an arithmetic number, because the mean of its divisors is an integer number (322176105).

Almost surely, 2^644352209 is an apocalyptic number.

It is an amenable number.

644352209 is a deficient number, since it is larger than the sum of its proper divisors (1).

644352209 is an equidigital number, since it uses as much as digits as its factorization.

644352209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 51840, while the sum is 35.

The square root of 644352209 is about 25384.0936217939. The cubic root of 644352209 is about 863.7229125649.

The spelling of 644352209 in words is "six hundred forty-four million, three hundred fifty-two thousand, two hundred nine".