Kim Kardashian showed off her sizzling curves in a bikini pic captioned, “This is 40!”

Friends and fans were quick to note that she defied stereotypes about the big 4-0. Kendall Jenner wrote, "sure is!" BFF Jonathan Cheban (AKA Foodgod) said 40 "looks better than 39!"

Several fans wrote, “How?” 

After just four hours up Monday, the post garnered 4.6 million likes. 

Last week, Page Six reported that the KKW mogul flew friends and family to a private getaway in the Caribbean.