644686439 has 2 divisors, whose sum is σ = 644686440. Its totient is φ = 644686438.

The previous prime is 644686429. The next prime is 644686499. The reversal of 644686439 is 934686446.

It is a happy number.

644686439 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644686439 - 2⁴ = 644686423 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644686429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322343219 + 322343220.

It is an arithmetic number, because the mean of its divisors is an integer number (322343220).

Almost surely, 2^644686439 is an apocalyptic number.

644686439 is a deficient number, since it is larger than the sum of its proper divisors (1).

644686439 is an equidigital number, since it uses as much as digits as its factorization.

644686439 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2985984, while the sum is 50.

The square root of 644686439 is about 25390.6762217945. The cubic root of 644686439 is about 863.8722264575.

It can be divided in two parts, 64468 and 6439, that added together give a palindrome (70907).

The spelling of 644686439 in words is "six hundred forty-four million, six hundred eighty-six thousand, four hundred thirty-nine".