Keyboard shortcuts as Numbers

I have read so many articles but am not getting exact answer what am looking for to implement. I am trying to enhance desktop application usability through shortcuts however am short of alphabets for page level shortcuts. So, am thinking to use numbers for Global Navigation as shortcuts.

• Is there a standard around we should have shortcut as Alphabets with any function keys? For ex: CTRL + P or ALT + F
• Can we use shortcut as numbers in place of Alphabets? For ex: CTRL + 3 or ALT + 4

Thanks in advance for all your ideas and inputs.