1 Jane Goodall: First we'll establish a baseline for communication based on basic mathematical principles. Base 2 arithmetic.
2 Steve: We're in their base! How're we gonna do that?!
3 Jane Goodall: All intelligent beings, anywhere in the universe, are able to count to two.
4 Steve: Well I dunno what hocus-pocus you got up your sleeve, but it's worth a shot.

For those for whom "base 2 arithmetic" is a foreign concept, I refer you to Wikipedia's article on binary numbers for quite a good primer. It's not too hard going, and the history bit is quite fascinating.

For those for whom "base 2 arithmetic" is second nature, I refer you to Wikipedia's articles on complex base systems and quater-imaginary base numbers to further expand and, quite possibly, blow your mind. Particularly check the arithmetic examples under "addition and subtraction", and "multiplication" for the latter.