644700809 has 8 divisors (see below), whose sum is σ = 683004960. Its totient is φ = 606438976.

The previous prime is 644700737. The next prime is 644700817. The reversal of 644700809 is 908007446.

It is a happy number.

644700809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644700809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644700869) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24062 + ... + 43224.

It is an arithmetic number, because the mean of its divisors is an integer number (85375620).

Almost surely, 2^644700809 is an apocalyptic number.

It is an amenable number.

644700809 is a deficient number, since it is larger than the sum of its proper divisors (38304151).

644700809 is a wasteful number, since it uses less digits than its factorization.

644700809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21159.

The product of its (nonzero) digits is 48384, while the sum is 38.

The square root of 644700809 is about 25390.9591981083. The cubic root of 644700809 is about 863.8786449533.

The spelling of 644700809 in words is "six hundred forty-four million, seven hundred thousand, eight hundred nine".