Viết chương trình để kiểm tra 1 số có phải là số nguyên tố

$\text{Program So_Nguyen_To;}$
$\text{Uses crt;}$
$\text{Var i,n : integer;}$
$\text{Begin}

$\text{Clrscr;}$
$\text{Writeln('KIEM TRA SO NGUYEN TO:');}$
$\text{Writeln('---------------------------');}$
$\text{Write ('Nhap so can kiem tra n = '); readln(n);}$
$\text{If ( n = 0 ) or ( n = 1 ) then}$

$\text{Writeln( n,' Khong phai la so nguyen to' )}$
$\text{Else}$
$\text{Begin}$
$\text{i:=1;}$
$\text{Repeat}$
$\text{i:= i+1;}$
$\text{Until (n mod i= 0) or (i*i>}$n);}$
$\text{If i*i>n then Writeln (n,' la so nguyen to')}$
$\text{Else Writeln (n,' khong phai la so nguyen to');}$
$\text{End;}$
$\text{Readln;}$
$\text{End.}$

uses crt;

var i,n,dem:integer;

begin

clrscr;

write('nhap so nguyen duong n ');readln(n);

dem:=0;

for i:=1 to n do if n mod i = 0 then dem:=dem+1;

if (n<2) or (dem< > 2) then writeln('n, khong phai la so nguyen to')

else if dem=2 then write(n,'la so nguyen to');

readln

end.

$#Zen$