644338799 has 16 divisors (see below), whose sum is σ = 708093792. Its totient is φ = 582709248.

The previous prime is 644338787. The next prime is 644338817. The reversal of 644338799 is 997833446.

It is a cyclic number.

It is not a de Polignac number, because 644338799 - 2²⁰ = 643290223 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644338799.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644335799) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 166187 + ... + 170019.

It is an arithmetic number, because the mean of its divisors is an integer number (44255862).

Almost surely, 2^644338799 is an apocalyptic number.

644338799 is a deficient number, since it is larger than the sum of its proper divisors (63754993).

644338799 is a wasteful number, since it uses less digits than its factorization.

644338799 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4106.

The product of its digits is 3919104, while the sum is 53.

The square root of 644338799 is about 25383.8294786267. The cubic root of 644338799 is about 863.7169207049.

The spelling of 644338799 in words is "six hundred forty-four million, three hundred thirty-eight thousand, seven hundred ninety-nine".