Perfect digit-to-digit invariant

In number theory, a perfect digit-to-digit invariant (PDDI; also known as a Munchausen number) is a natural number in a given number base $b$ that is equal to the sum of its digits each raised to the power of itself. An example in base 10 is 3435, because $3435\; =\; 3^3\; +\; 4^4\; +\; 3^3\; +\; 5^5$. 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. Provided by Wikipedia