I agree it should be aliased, but I think it should be the other way around. The reason being that we already have dozens of related tags which feature the numeral and not the word for the # of things. And it's better for tags if they follow a pattern system so that it's easier to guess and to remember.
We have (just to list a few of them):
5_toes (1207) vs five_toes (2)
5_fingers (592) vs five_fingers (4)
4_toes (5068) vs four_toes (23)
4_fingers (426) vs four_fingers (3)
4_arms (27) vs four_arms (104)
3_toes (2565) vs three_toes (1)
3_fingers (436) vs three_fingers (3)
2_toes (199) vs two_toes (0)
2_fingers (6) vs two_fingers (0)
Obviously, people use the numeral version of the tags far more often than the word version. I think there's several reasons why.
Not to mention, the numeral avoids confusion with other tags based on the word like threesome, foursome, and prevents homonyms mistakes like "four_arms" getting tagged "fore_arms"/"forearms" which is easier to do when using the word instead of the numeral. The use of a numeral helps create one more layer of differentiation between them.
And it makes for shorter tags.
And many people find numerals easier to read at a glance.
And because of alpha-numeric numbering systems, it means all the [number of]_[tag] type tags get listed together at the top of the general tags list on an image, making them easy to spot, check for if they're tagged yet, and double check to make sure they're correct, etc.
ETA: I also just realised that there's a character apparently named Four Arms from something called ben_10. It does have a character tag of its own , but that is one more potential tag confusion if we make the official tag "four_arms" instead of "4_arms" since it can be confused with the character.
Updated by anonymous