644312665 has 8 divisors (see below), whose sum is σ = 818656200. Its totient is φ = 485129472.

The previous prime is 644312623. The next prime is 644312671. The reversal of 644312665 is 566213446.

It can be written as a sum of positive squares in 4 ways, for example, as 11689561 + 632623104 = 3419^2 + 25152^2 .

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 644312665 - 2¹¹ = 644310617 is a prime.

It is an unprimeable number.

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, 3789990 + ... + 3790159.

It is an arithmetic number, because the mean of its divisors is an integer number (102332025).

Almost surely, 2^644312665 is an apocalyptic number.

It is an amenable number.

644312665 is a deficient number, since it is larger than the sum of its proper divisors (174343535).

644312665 is a wasteful number, since it uses less digits than its factorization.

644312665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7580171.

The product of its digits is 103680, while the sum is 37.

The square root of 644312665 is about 25383.3146968634. The cubic root of 644312665 is about 863.7052432648.

The spelling of 644312665 in words is "six hundred forty-four million, three hundred twelve thousand, six hundred sixty-five".