program phuongt; uses crt; var n, s, i: integer; begin clrscr; write('Nhap n = '); readln(n); s:=0; i:=1; if n<2 then write(n, ' khong phai so nguyen to'); if n=2 then write(n, ' la so nguyen to'); if n>2 then while i<=n do begin if n mod i = 0 then s:=s+1; i:=i+1; end; if (s=2) then write(n, ' la so nguyen to') else write(n, ' khong la so nguyen to'); readln end.
