Graham's Number is not noteworthy because it's head-imploding, it's noteworthy because it's one of the few head-imploding numbers that is actually used for something constructive. There are literally an infinite amount of head-imploding numbers: Graham's Number is not special in that regard.
Also, as a side note, I think you can use a carat (^) instead of those awkward arrows; they are more commonly used and can be typed much easier. I could be wrong about that but I don't think I am.
edit: Turns out the arrows are for implied repeated multiplication or something. I think. I'm not sure why they do it but I don't presume to know more than mathematicians. Disregard the above sentence.