This is a case where a bit of skeuomorphism (gasp) might have been useful. The momentary screen refresh flash on old-style LCD calculators helped indicate to the user that the input had been acknowledged. In the iOS calculator, the subtle darkening of the "=" button (which is also almost entirely concealed by the rest of the curled thumb in right-handed users) is just not enough feedback on its own.
I don't think you mean skeuomorphism, but the point is valid. There should be some sort of action indication. It's really pretty bad design.
I bet Jony Ive & Co. consider that "unnecessary ornamentation".
729 divided by 27 equals 27.
That is why if you tap "=" its still displaying 27 and if you tap it again it divides by 27 and a 1 is displayed.
So the Calculator is working fine.
It might have been a joke.
Yes you are right. I also thought about this.
Calculator is working fine, UX is pretty bad.
So the answer you get is the same as you've typed in (27). Hardly "can't divide" ...