How do I stick a period in the middle of a string?

I have an integer, for example 123456, and I need to display it as 1234.56 as in currency format. I've tried doing an x.ToString("0.00") but it adds a '.00' at the end (i.e. 123456.00) and x.ToString("#.##") doesn't seem to do anything at all. How is this done? Thanks in advance.