Quote Originally Posted by krishna View Post
I am sorry , i mean to say , that in my project i am trying to find a method by which we can find the factor of a number which is product of 2 prime number and we dont know those two number but we we know their product....
You are wasting your time and our time, logarithms will not (very high probability) help you.

But any of the CASs described in the posts in this thread will give arbitrary precision logarithms if you must pursue this line.