It has 2 cylinders. I am attaching the link to the official Ducati page where it explains in detail the engine. But here are the basics...
L-twin cylinder
2 valves per cylinder
air cooled
Displacement 618 cc
Bore x Stroke 80 x 61.5 mm
Compression Ratio 10.5:1
Power* 46.4 kw - 63 hp @ 9500 rpm
Torque* 5.7 kgm @ 6750 rpm
Fuel injection Marelli
2 aluminium mufflers