program so_nguyen_to;
uses crt;
var i,n,dem:integer;
begin clrscr;
write('Nhap so 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 writeln(n, 'la so nguyen to');
readln;
end.
Học tốt!