As it turns out, any figure which has point symmetry exhibits rotational symmetry around that point of symmetry. So, letters which have point symmetry will have rotational symmetry for sure. So, the letters that will fall under this category are:

H, I, N, O, S, X, Z

But we can’t be sure that these are the only letters which have rotational symmetry. A letter with rotational symmetry may not have point symmetry. Fortunately, there are no alphabets like that. So, 7 is the answer.