It is generally believed that infinity cannot be treated as a number. Otherwise, we would arrive at contradictions like this famous one:
And we subtract from each equation,
However, why did we subtract only from each equation? If as we first said, then couldn't we subtract from the first equation, from the second, and from the third? We wouldn't be breaking an algebraic rules, because all of these amounts are equal to each other. Then, we would get which is perfectly true!
The moral of the story: treat infinity carefully! It isn't exactly a number, but if we take certain precautions, then we can use as if it were a number.
Please note however that this again represents curious exploration, not rigid proof.
I would welcome any thoughts, comments, or objections!