I doubt that there's any virtue in round numbers, but it's not a silly question at all. I have a book that has 32 chapters (or maybe 32 +1) because that's the number of paths on the Qabalistic Tree of Life, and it's relevant to the novel. Also how many tteh we have, adn pinal vertabrae...except for our little tailbone vertaba, which makes it 32 +1 again...)
There's no optimum number, but some critics like Grumpy Old Bookman say the first thing they do is divide the number of pages by the number of chapters and look for a low number. I think this is a crappy guide, as many bad books, like
The Da Vinci Code, have relatively few pages and a zillion chapters. But some folks pay attention to it.
Unless I had some specific thematic design, though, I wouldn't worry about this until the book was finsihed and fully revised. But thinking about it isn't crazy. Premature, maybe.
And, as Maestrowork points out, 42 is worth thinking about. If I recall, In Douglas Adams'
Hitchiker's Guide to the Galaxy, 42 turns out to be The Answer. (The problem is that no one knows the question.)