Theory:

LibreOffice Calc is the spreadsheet part of LibreOffice.
 
Spreadsheets enable us to organise, analyse, and store data in tabular form. Furthermore, in a spreadsheet, we can manage this data to produce specific results.
 
LibreOffice Calc  - Formatting cells using Shortcut keys:
 
Below is a list of LibreOffice Calc keyboard shortcuts.
 
Shortcut Key
Effect
\(Ctrl+Shift+1 \)
Two decimal places, thousands separator
\(Ctrl+Shift+2 \)
Standard exponential format
\(Ctrl+Shift+3\) 
Standard date format
\(Ctrl+Shift+4\) 
Standard currency format
\(Ctrl+Shift+5 \)
Standard percentage format (two decimal places)
\(Ctrl+Shift+6 \)
Standard format
\(Ctrl+1 \)
Open Format Cells dialog
Note: Do not use the numbers on the number pad.
Reference:
https://help.libreoffice.org/4.4/Calc/Shortcut_Keys_for_Spreadsheets