Citigroup Inc. was able to shuck part of its insurance arm Primerica Inc. through an initial public offering of the unit Thursday. The company's stock closed at $19.65 a share on the New York Stock Exchange, up 31% from its IPO price of $15. Citigroup sold 21.4 million shares in the offering, 3.4 million more than originally planned, pricing them above its expected $12 to $14 range.

Citigroup's own shares rose slightly Thursday, closing at $4.18, up 3.2%.

Concurrent with the IPO, Citigroup sold 17.2 million shares to private-equity funds managed by Warburg Pincus LLC at the offering price, along with warrants to buy about 4 million more.

Post-IPO, Citi owns 43% of Primerica's common shares; the company said it intends to divest its remaining interest in the unit "as soon as is practicable."

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