Apple this week hit a pretty mind-boggling milestone: the 25 billionth song was downloaded on iTunes on Wednesday.That’s billion with a ‘b’, which is a bit hard to imagine, but to put it in perspective, it’s roughly equal to three-and-a-half songs for every person on the face of the earth. That’s a lot of music.Compare that to the top-selling song of all time according to the Guiness Book of World Records which is “White Christmas”. It has sold around 100 million copies. Multiply that by 250 and you get 25 billion.Michael Jackson’s “Thriller” is still the number one selling album of all time with more than 42 million records sold. Do that times 600 and you’ll get to 25 billion.So, who was the lucky 25-billionth-downloader and what song did he or she buy? It was Phillip Lupke of Germany who purchased “Monkey Drums (Goksel Vancin Remix)” by Chase Buch, a British DJ who’s apparently pretty well known on the house music scene.Still, the song’s not nearly as popular as the 25 millionth song downloaded in 2003, which was “Let It Snow! Let It Snow!” by Frank Sinatra or the one billionth tune bought in 2006 which was “Speed of Sound” by Coldplay.For making his purchase at just the right time, lucky Mr Lupke will receive a 10,000 Euro ($13,528) iTunes gift card, which will buy him all the house music he can handle.