With some rarer ones (eg. slovene), you even have a special dual form (singular, dual, plural).
And then there are different declinations when eg counting:
eno pivo (1 beer)
dve pivi (2 beers, dual)
tri piva (3 beers, plural)
štiri piva (4 beers, plural)
pet piv (5 beers, plural, but now in genitive case for some reason, same for higher numbers, eg sto (100) piv)
On the other hand, knowing slovene and being able to read (usually the serbian form of) cyrillic makes you understand 2/3 of the russian texts out there, which is especially useful for dodgy forums with semi-legal knowledge not available anywhere else and which google can't/won't fully translate (unless you copy-paste the text into a translation window).