Y Combinator co-founder Paul Graham tweeted today that YC’s 380 companies (prior to the current batch) have raised $1,048,274,000. Y Combinator, which launched in 2005, takes on two classes of startups per year into their three month program, during which they mentor and connect the founders and invest in the companies.

The total amount of funding raised by the 380 companies prior to the current YC batch is $1,048,274,000.

— Paul Graham (@paulg) July 25, 2012

Even the simplest of mathematicians can look at the two numbers and divide the larger by the smaller and infer that, on average, Y Combinator companies raise more than $2,759,000. But not all YC companies are created equal. Two of Y Combinator’s most notable alums, Dropbox ($257 million) and Airbnb ($120 million), account for almost 36% of the impressive funding total.

When you add in other well-funded companies, like Scribd ($25.8 million), Disqus ($10.5 million), and Posterous ($10.1 million), the total for the remaining 375 Y Combinator companies is still an enormous, but significantly diminished, $624.9 million.

This is the latest eye-popping number from Y Combinator, following Forbes’ report in April that Y Combinator companies were worth a total of $7.78 billion.