**abcdef**, with distinct digits between 1 and 9. A close inspection of the digits reveals that

**abcdef**,

**cdef**, and

**def**are all prime numbers.

If I turn the calculator upside-down, I see that **uvwxyz** and **wxyz** are also prime numbers.

Which number is displayed in the window of my pocket calculator and what is the upside-down version of it?

*Full credit for this problem goes to Ajit Athle who has very kindly given his permission for the puzzle to be posted here.*