"The Insider" has your box office scoop...

College card-counting movie '21' was tops at the box office this weekend, as it premiered in first with $23.7 million.

The film follows a group of MIT brainiacs who join a card-counting scheme and make millions at Las Vegas casinos. The film stars KATE BOSWORTH, JIM STURGESS, KEVIN SPACEY, LAURENCE FISHBURNE, AARON YOO and LIZA LAPIRA.

'Horton Hears a Who!' dropped to second with a still-strong haul of $17.4 million. JIM CARREY, in his second DR. SEUSS film (he also starred in 'How the Grinch Stole Christmas') plays an elephant who learns that a planet containing a village called "Who-ville" is located on an infinitesimal grain of dust and it's up to him to protect the people who live there. STEVE CARELL, DANE COOK, SETH ROGEN, CAROL BURNETT, JAIME PRESSLY, ISLA FISHER, JONAH HILL ('Superbad'), WILL ARNETT ("Arrested Development") and AMY POEHLER ("Saturday Night Live") also provide voices.