644646439 has 2 divisors, whose sum is σ = 644646440. Its totient is φ = 644646438.

The previous prime is 644646433. The next prime is 644646451. The reversal of 644646439 is 934646446.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644646439 - 2²⁵ = 611092007 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644646433) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322323219 + 322323220.

It is an arithmetic number, because the mean of its divisors is an integer number (322323220).

Almost surely, 2^644646439 is an apocalyptic number.

644646439 is a deficient number, since it is larger than the sum of its proper divisors (1).

644646439 is an equidigital number, since it uses as much as digits as its factorization.

644646439 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1492992, while the sum is 46.

The square root of 644646439 is about 25389.8885188573. Note that the first 3 decimals coincide. The cubic root of 644646439 is about 863.8543595785.

The spelling of 644646439 in words is "six hundred forty-four million, six hundred forty-six thousand, four hundred thirty-nine".