How To: Split file by # of lines in text file?

I have 4 text files with millions of newlines that I am trying to split. I would like to split each of these files into new files if the count of newlines is less than 65530 (just padding a bit from 2¹⁶ limit).

Would anyone be able to provide me a bit of direction on this? I am eager to learn.

Please and thank you!