In number theory, a perfect digit-to-digit invariant is a natural number in a given number base that is equal to the sum of its digits each raised to the power of itself. For example, in base 3 (ternary) there are three: 1, 12, and 22. The term "Munchausen number" was coined by Dutch mathematician and software engineer Daan van Berkel in 2009, as this evokes the story of Baron Munchausen raising himself up by his own ponytail because each digit is raised to the power of itself.
