644064909 has 4 divisors (see below), whose sum is σ = 858753216. Its totient is φ = 429376604.

The previous prime is 644064877. The next prime is 644064913. The reversal of 644064909 is 909460446.

644064909 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 644064909 - 2⁵ = 644064877 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644064919) 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, 107344149 + ... + 107344154.

It is an arithmetic number, because the mean of its divisors is an integer number (214688304).

Almost surely, 2^644064909 is an apocalyptic number.

It is an amenable number.

644064909 is a deficient number, since it is larger than the sum of its proper divisors (214688307).

644064909 is a wasteful number, since it uses less digits than its factorization.

644064909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214688306.

The product of its (nonzero) digits is 186624, while the sum is 42.

The square root of 644064909 is about 25378.4339351348. The cubic root of 644064909 is about 863.5945229051.

The spelling of 644064909 in words is "six hundred forty-four million, sixty-four thousand, nine hundred nine".