To use Google's built-in calculator function, simply enter the calculation you'd like done into the search box and hit the Enter key or click on the Google Search button. The calculator can solve math problems involving basic arithmetic, more complicated math, units of measure and conversions, and physical constants.
I think it is awesome because this makes it possible to perform high precision arithmetic on portable devices like PDAs and mobile-phones which are very restrictive otherwise.
BTW, the largest factorial I could find using Google's Calculator was of 170.
What is the range of the numbers that the Google Calculator can store?