This is a very energy-efficient bulb, perfect if you're trying to keep energy costs down. The socket on the bulb is the quite common E27 socket, also referred to as an intermediate socket.
From Amazon
Philips Hue Ellipse White and Colour Ambiance LED Smart Light Bulb [E27 Edison Screw] for Indoor Home Lighting. Bedroom, Livingroom and Dining.
Philips Hue
Ellipse - E27 smart bulb