Prime Numbers

x/log(x) (red) Approximates the Number of Primes under xx/9 (blue)The green line shows the difference

Playing with a little bit of algebra and trying to write a program to solve a particular problem. I need to factor a number, which means I need a list of prime numbers, so how much space do I need given a number of certain size? x/9 (blue) approximates x/log(x) well enough for my purposes for values of x under a billion.

P.S. Finished my factoring program.