Prime of Prime

Because my brain is weird and comes up with strange questions, is there an equation that can come up with answers that are not only prime numbers but have digits that are also only prime numbers? Such as 11. It is a prime number that consisting of prime numbers. 13, 17, and 21 are such examples of prime numbers whose digits are also prime numbers. And, as I mentioned earlier because my brain is weird, it decided there needs to be a name for prime numbers made up of only prime digits; it came up with Super Prime.

Oh, and for the record, the 500th prime number is 3571, making it a Super Prime.

Or, perhaps I shall call them Prime Squared because I just thought of a third category of Prime Numbers. One where not only are the single digits prime themselves, but any number of combinations of those digits are themselves still prime. So, Prime Cubed.

And you know what the kicker is? I both hate math and suck at it.