Test prime number - Pascal program language

Program Test_prime_number;
Uses crt;
Var
   number, i:  Longint;
Begin
   Clrscr;
   write('Enter the number you want to test: ');
   Readln(number);
   i := 2;
   If number <= 1 Then Write('Condition: number> 1');
   If (number < 4) And (number > 1) Then write('This is a prime number!')
   Else
      Begin
         While (number Mod i <> 0) Or (i < number Div 2) Do
            i := i+1;
         If number Mod i <> 0 Then write('This is a prime number!')
         Else write('Is not a prime number')
      End;
   Readln;
End.