I've been kicking this question around in my head for a while: Why exactly do Slavic languages make nouns that follow numerals typically take the Genitive, depending on the situation? I understand that this is simply what is done, but that still leaves me curious. Is there an actual reason for this, or is this something that is as easy to answer as why the word for "sun" is masculine in Spanish, feminine in German, and neuter in Russian? (I.e., no one knows)
EDIT: I should be more specific. I know that nouns do change, specifically in Russian that after 2-4, it takes the Genitive singular, whereas 5-21 & etc, it would be Genitive plural. My question is why is it that it becomes Genitive when it is no longer singular? Is there any reason, or has it merely become a convention of Slavic languages? Do other case-heavy Indo-European languages do this, specifically Satem branch languages?
