{first 10-digit prime found in consecutive digits e}.com.

So read a billboard placed this week in the heart of Silicon Valley, which posed a complex question and opened the doorway to a mathematic treasure hunt - all designed by Google to find genuises so they can hire them.

"The answer, 7427466391.com, would lead a puzzle-sleuth to a Web page with yet another equation to solve, with still no sign the game was hosted by Google. Mastering that equation would lead someone to a page on Google Labs, the company's research and development department, which reads: "One thing we learned while building Google is that it's easier to find what you're looking for if it comes looking for you. What we're looking for are the best engineers in the world. And here you are."