644599009 has 4 divisors (see below), whose sum is σ = 647838400. Its totient is φ = 641359620.

The previous prime is 644598991. The next prime is 644599049. The reversal of 644599009 is 900995446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 644599009 - 2²⁷ = 510381281 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 644599009.

It is not an unprimeable number, because it can be changed into a prime (644599049) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1619397 + ... + 1619794.

It is an arithmetic number, because the mean of its divisors is an integer number (161959600).

Almost surely, 2^644599009 is an apocalyptic number.

It is an amenable number.

644599009 is a deficient number, since it is larger than the sum of its proper divisors (3239391).

644599009 is a wasteful number, since it uses less digits than its factorization.

644599009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3239390.

The product of its (nonzero) digits is 349920, while the sum is 46.

The square root of 644599009 is about 25388.9544684298. The cubic root of 644599009 is about 863.8331729690.

The spelling of 644599009 in words is "six hundred forty-four million, five hundred ninety-nine thousand, nine".