World's Most Expensive What is the most expensive mobile number in the world? Announced by the Kuwaiti News Agency, the world's most expensive mobile number was auctioned for charity in Qatar on May 22 2006. The number sold for 10m Qatari riyals or £1.5m. The number, would you believe, was 666-6666. The auction was organized by national telco Qtel that has held two previous auctions and is p! lanning on another one in September. In the beginning, there were eight individuals bidding on this unique number but it finally dwindled down to last souls.