You cannot have an example of infinity in numerical form because you cannot assign it a value, because once you do it is no longer infinite, it's a specific number.

An irrational number can be an example of infinity in the sense that the decimal values never stop, however the number itself is a specific location on the number line.

If you want to think about it in some terms, think of it like this:
Pi is still a number on the number line, so it's value is (somewhat) known. Infinity encompasses every point on the number line at the same time, so you could even say that the number line itself would be an example of infinity.