ASUS Ultrabook numerical keypad

Look for a NumLock secondary Fn Key. Each model is a little different, so without your specific model number I can't say for sure.

For example, on the Asus U36, the Numlock shares a button with Insert (top right on keyboard). To activate the keypad buttons, you'd hold down Fn + Insert to activate the 10 key that is integrated into the keyboard.

The Fn key is on the bottom left of the keyboard next to the Windows button.
 

Function key plus num/lck or fn/numlock

Sorry, didn't see previous answer