Definition:Perfect Digit-to-Digit Invariant/Also known as

Perfect Digit-to-Digit Invariant: Also known as
A perfect digit-to-digit invariant is also known as a Münchhausen number.

This comes from the idea that these perfect digit-to-digit invariants "raise themselves" similarly to how raised himself by riding a cannonball in the $1943$ film.

Some sources render the name as Munchausen, with or without the.