Here is a list of Excel shortcuts starting with "Ctrl" and ending with a number from 0 to 9 except 7. Shortcut "Ctrl+7" is not assigned.

What to doShortcuts
Hide the selected columnsCtrl + 0
Display "Format Cells" dialog boxCtrl + 1
Bold text or remove bold formattingCtrl + 2
Italicize text or remove italic formattingCtrl + 3
Underline text or remove underlineCtrl + 4
Apply or remove strikethrough formattingCtrl + 5
Hiding and displaying objectsCtrl + 6
Not assignedCtrl + 7
Display or hide the outline symbolsCtrl + 8
Hide the selected rowsCtrl + 9