There is often this misconception that in order for your pages to rank, you need at least 500 words on a page or some other number.
That is not true. Ranking is dependent on a ton of factors, and while more words on a page may help Google understand the relevance of the page to the query - it doesn't necessarily mean the page will rank.
A Google Webmaster Help thread has John Mueller, a Google representative, talking just about that.
Rest assured, Googlebot doesn't just count words on a page or in an article, even short articles can be very useful & compelling to users. For example, we also crawl and index tweets, which are at most 140 characters long. That said, if you have users who love your site and engage with it regularly, allowing them to share comments on your articles is also a great way to bring additional information onto the page. Sometimes a short article can trigger a longer discussion -- and sometimes users are looking for discussions like that in search. That said, one recommendation that I'd like to add is to make sure that your content is really unique (not just rewritten, autogenerated, etc) and of high-quality.
So clearly John is saying there is no magic number - the most important thing is how unique and valuable that content is.
Forum discussion at Google Webmaster Help.
Image credit to BigStockPhoto.