Exterior of mall Alderwood Mall in the Seattle suburb of Lynwood, WA is among more than 125 retail properties in GGP’s portfolio.

CHICAGO—GGP Inc. on Monday confirmed that it had received an unsolicited bid from Brookfield Property Partners (BPY) to acquire the outstanding shares of the mall REIT that it doesn’t already own. At $23 per share, the deal would be valued at approximately $14.8 billion.