Stewart Cook / Rex USA 1 / 6
Stewart Cook / Rex USA 1 / 6

On Sept. 23, Justin Timberlake rocked his body in Las Vegas at his bachelor party!

Timberlake, 31, was the guest of honor among a group of 20 men who "took over the dance floor table" at Tryst nightclub at the Wynn Las Vegas, a rep for the venue tells Us Weekly.

Wearing a bow tie and a fedora, the "Trouble With the Curve" star and his posse sipped cocktails and Timberlake's own liquor, 901 Tequila, as they grooved until the wee hours to the sounds of DJ Spider. "The group was very polite," the rep says.

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(Another star at Tryst on Thursday? Ryan Seacrest, hanging out separately with two pals, by Tryst's 90-foot waterfall.)

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Although the club was packed with models, Timberlake "was a good boy," an eyewitness tells Us. "It was just him and his guys."

Back in January, Us Weekly broke the news that Timberlake had proposed to longtime love Biel, 30, in the mountains of Jackson, Wyo., in late December 2011.

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Dating for five years, the couple have been tight-lipped about exactly when and where they'll wed. Back in July, Biel said she had done "almost nothing" to prepare for the big day.