644444399 has 8 divisors (see below), whose sum is σ = 667000320. Its totient is φ = 621999000.

The previous prime is 644444393. The next prime is 644444431. The reversal of 644444399 is 993444446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644444399 - 2²⁸ = 376008943 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644444393) 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 in 7 ways as a sum of consecutive naturals, for example, 15677 + ... + 39174.

It is an arithmetic number, because the mean of its divisors is an integer number (83375040).

Almost surely, 2^644444399 is an apocalyptic number.

644444399 is a deficient number, since it is larger than the sum of its proper divisors (22555921).

644444399 is a wasteful number, since it uses less digits than its factorization.

644444399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55261.

The product of its digits is 1492992, while the sum is 47.

The square root of 644444399 is about 25385.9094578075. The cubic root of 644444399 is about 863.7641026765.

Adding to 644444399 its sum of digits (47), we get a palindrome (644444446).

The spelling of 644444399 in words is "six hundred forty-four million, four hundred forty-four thousand, three hundred ninety-nine".