Bit late my comment and my apologies if I say something that is already mentioned somewhere else as I hope you find it relevant,...
I know from experience it's not about numbers in general. We use in our URL page naming numbers a lot, as the name of the files refers in our case to an actual model name,which contains a number.
It is more that you need to make sure:
you do not use too many parameters in your URL. The maximum that seems to be excepted is 2 parameters.
Do not use too general parameters, like ID will be ignored by Google it thinks it's a session ID.
Although not all experts agree on this; you should not use _ in the naming of your files or media like images, it is better to use - .
The naming should be inline with what the page talks about, so basically the title(s) of the document
And last but not least even the type of domain (.com, .org, etc...) has influence on the ranking.
You can find a lot of useful info here:
http://www.googlerank.com/ranking/Ebook/urlwords.html
http://www.mattcutts.com/blog/dashes-vs-underscores/
