I found this over at the Inquirer:

According to top mathematicians, the best-known example of a pure sinatra number is 14,991,338,361,953,636,352, although partial sinatra numbers are known to exist too. Sinatra numbers are one of Single Mother Nature�s wonders, having special and unusual properties that make them unlike non-sinatra numbers. To investigate these properties, you need to display the sinatra number in hexadecimal format. Like the Windows calculator can.