I need an optimal algorithm to find the largest divisor of a number N. Preferably in C++ or C#

Question

I am currently using the following code but its very slow for large numbers

        static int divisor(int number)
        {
            int i;
                    


        

Answer 1

Some additional optimizations:

1.  If even then divisable by 2.
2.  If the sum of the digits is divisable by 3, then number is divisble by 3 (ie 78 = 7 + 8 = 15 = 1 + 5 = 6 which is divisable by 3)
3.  If it ends in 0 or 5 it is divisable by 5

Gordon.