Is a 23 on the ACT good enough?

I recently took the ACT at my school and got a 23. I am very satisfied with it and want to apply to Howard University my senior year. Some people told me to retake it and others said a 23 is really good. I also have a 3.5 or 4.3 GPA and recently got inducted into the National Honor Society. Is this good enough to get into Howard or any other good school i.e. U of I Urbana-Champagne?