Câu 2:
program ct;

uses crt;

var i,n:integer;

begin

clrscr;

write(‘nhap n:=’);readln(n);

if n<=1 then writeln(‘N khong la so nguyen to’) else

begin

i:=2;

while (n mod i<>0) do i:=i+1;

if i=n then writeln(n,’ la so nguyen to’); else

writeln(n,’khong la so nguyen to’);

end;