Entertainment

Harry Potter and the Chamber of Commerce

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Hordes of pen-waving, braces-wearing, photo-taking girls are crowded on 45th Street, clutching Playbills like rosaries, waiting for the most famous 21-year-old in the world to emerge from the stage door. They surge forward as a bodyguard shows his face, followed by Daniel Radcliffe, a k a Harry Potter a k a J. Pierrepont Finch, the upstart mogul of Broadway’s “How to Succeed in Business Without Really Trying.”

Radcliffe, fresh from a preview performance of the classic 1961 musical at the Al Hirschfeld Theatre, cheerfully poses for pictures, signs posters and indugles questions.

“Are you going to get a Tony?”

“I don’t think so, but thank you for your optimism!”

“Why are you so cool and not an a – – hole like so many other actors?”

“Uh, a lot of [actors] are pretty cool. But some are a – – holes.”

“Will you sign my tie?”

“Of course.”

As the bodyguard swiftly but subtly removes a young woman’s claw-like grip from Radcliffe’s shoulder, he strolls through the scrum like a young prince, untouched by the mania. A sensation since landing the role of Harry at 10, the frenzied and sometimes frightening attentions of tweens is now routine.

He signs his last autograph, then hops into a giant black Denali and speeds off. A grown woman who just missed getting his signature nearly breaks into tears.

As the Harry Potter franchise wraps with the July 15 release of “The Deathly Hallows: Part 2,” Radcliffe can no longer play the naif — he’s a tycoon worth an estimated $67 million, with a portfolio of NYC properties ranging from a $4.3 million Mercer Street loft to a $5.6 million West Village townhouse, plus the TriBeCa apartment he lives in, a $5 million job on Morton Street. Unlike his character in “How to Succeed,” who fails upward, Radcliffe has strategically amassed a small fortune, making him the fifth richest person under 30 in his native England, according to London’s Sunday Times.

“He’s a model for other actors and sports figures who often end up with zero later in life,” says Lew Altfest, CEO of Altfest Personal Wealth Management. “Child stars get caught up in Hollywood, and what they need to do is put the money away and not touch it. But that’s very hard to do, especially for someone that age.”

How to Succeed in Business? Be Daniel Radcliffe.

Or perhaps be born to his parents, casting director Marcia Gresham and literary agent Alan Radcliffe. His mother is the driving force behind his New York real estate bonanza, sources say. His New York apartments — he also has a London flat — are in her name or one of the companies she has formed for Radcliffe since he landed the Potter gig.

“She was very sweet and very business-like,” says one person familiar with the Morton Street deal, who describes the 2,500-square-foot apartment and its sweeping river views as “glorious.” “I got the impression they were investing in real estate in the city. She seemed to know exactly what she was doing.”

“The closing was super-fast,” says Ann Emonts, who sold her 12th Street townhouse to Gresham in 2009. She said the house, built in 1847 by a sea captain, is “absolutely charming.” Currently under a gut renovation, the house also boasts “one of the better gardens in the city.”

“I couldn’t tell anyone who I was selling it to,” Emonts says, “but it was sort of a fun secret.”

With millions in the bank and a huge bachelor’s lair at his disposal, Radcliffe could capitalize on his fame by throwing lavish parties and romancing an onslaught of hotties. Instead, he spends most of his time holed up on Morton Street, watching the History Channel with his girlfriend of nine months, Olive Uniacke, he recently said.

Maybe he and Charlie Sheen need to have a wizard-to-warlock chat.

“He’s really down to earth,” says Radcliffe pal Our Lady J, a cross-dressing singer who met the actor and his parents at a party in 2008. “I was surprised at how normal he is. You hear about these child stars who are crazed with fame. He’s just really interested in his craft.”

The two hit it off talking about American politics and religion. “He seems to be really interested in learning about new things. He’s like a sponge,” J says.

And while the rest of the “How to Succeed” cast head out in groups to enjoy themselves after a 12-hour day at the theater, Radcliffe keeps to himself, sometimes leaving in the company of Uniacke, the step-daughter of “Harry Potter” producer David Heyman.

“He doesn’t go out with the rest of the cast after the show,” says a “How to Succeed” insider. “He heads home each night.”

“He can’t, really. He’d be mobbed,” adds cast member Rob Bartlett. “Although we’d love for him to come out with us.”

Radcliffe spends his spare time listening to the Sex Pistols, Radiohead and the Libertines, but he’s also fond of singing Tom Lehrer’s 1959 science-nerd anthem “The Elements,” which lists every known entry in the periodic table, circa 1959. He reads everything from novels by Vladimir Nabokov to essays by Fran Lebowitz, one of which he recently read out loud to a handful of his “How to Succeed” castmates.

He also buys modern art, including a Jim Hodges painting called “Mona D, Mary And Me” which he purchased for himself on his 18th birthday, according to London newspaper The Guardian.

The whiz kid grew up an only child in London’s Fulham area. With his casting agent mother to guide his career, he landed a spot in the BBC’s 1999 production of “David Copperfield,” which he parlayed into the role of a lifetime.

Now the Harry Potter brand is worth some $24 billion, and Radcliffe reportedly earned $41 million for the final two films, putting his fee in the vicinity of Tom Cruise and Will Smith. So important is he to the franchise that Warner Brothers bought out the Hirschfeld for five nights — a cost of about $500,000 — so that Radcliffe could take time off to promote “Harry Potter and the Deathly Hallows: Part 2.”

Now of drinking age and living on his own, Radcliffe still works closely with his parents, who attend every performance of “How to Succeed,” according to the insider.

“They’re really sweet,” says J of Radcliffe’s folks. “I think they’re the reason he’s so down to earth. They’re the kind of people who look you in the eye. They are very perceptive and very kind. They don’t really like to be in the spotlight.”

Following the show last week, his parents slipped out before him, hopped in the Denali, and waited as their son tended to his groupies. His mother’s all-business attitude apparently rubs off on her only child.

“He is so hard-working,” says Bartlett, who plays both Wally Womper and Mr. Twimble. “He’s completely professional. This is not an example of marquee stunt casting.”

Although “How to Succeed” has yet to be reviewed, Radcliffe will likely win raves similar to those he got for 2008’s “Equus.” Previews reveal that Radcliffe has developed a spot-on American accent, hitting every note and nailing his dance routines with surprising groove. Not that his fans would care. The minute the 5-foot-5-inch star descends on the stage via ropes — he plays a window washer-cum-executive — the crowd goes wild. They don’t stop cheering until the final scene.

“He has an amazing voice! I didn’t expect him to be so great!” said President of the Hunter College Harry Potter Fan Club Christina Lio, 22, as she stood in the cold outside the theater. “He’s just so adorable.”

stefanie.cohen@nypost.com