GeoGebra has built-in tools for computing factorials, permutations and combinations, just like your calculator. 
     GeoGebra Instruction 1
Open CAS under  
View in  
Menu. 
To         compute         a         factorial,         type         your         number         immediately         followed         by         “!”         and         press         Enter.         
To         compute         permutations,         type         nPr.         Select         the         command         nPr(<n>,     <r>).         Enter         the         total         number         of         elements,         and         then         the         number         of         elements         to         be         drawn         from         the         total.         Press         Enter.         
To         compute         combinations,         type         nCr.         Select         the         command         nCr(<Number     n>,     <Number     r>).         Enter         the         total         number         of         elements,         and         then         the         number         of         elements         to         be         drawn         from         the         total.         Press         Enter.