Display week number in the standard system tray clock? Not that I can see, but there are many different ways to display the information presented. Go to Control Panel> Language> change formats to see what's available. You may need a 3rd-party clock/calendar to get that type of display. Good luck.
For the record, I found T-clock which allows for customized formats. Really an excellent piece of software but with one drawback; hovering over it does not make calendar pop up.