The math-whizzes-turned-gamblers film “21” was the top-earning movie at the box office for the weekend ending March 30, generating an estimated $23.7 million in its debut weekend. It set back “Dr. Seuss’ Horton Hears a Who!” which had grabbed the top spot for the previous two weekend. The movie “21,” about a team of college math geniuses assembled by a professor played by Kevin Spacey to beat the Las Vegas blackjack tables, was released by Columbia Pictures.

“Horton” (20th Century Fox), in second place, grossed $17.4 million for a three-week total of $117.2 million, according to the box-office tracking company Media by Numbers. Third place went to the satirical “Superhero Movie,” which drew $9.5 million in its opening weekend. “Tyler Perry’s Meet the Browns” (Lionsgate), last weekend’s second-ranking film, dropped to fourth place with $7.7 million its second week, followed by another comedy, “Drillbit Taylor” (Paramount), with $5.8 million in its second week.