In Metropolis, all bus routes are numbered with a number >10, but not all numbers are used.
Buses 33, 55, 222, and the special 55555, and only those buses, go to the airport. All the buses that go to the airport, and only those buses, are numbered such that all digits are the same. The local taxi service (phone #777-7777) also goes to the airport.
What is a concise way of describing a number with multiple digits that are all the same digit?
Under 100, I would call them "multiples of 11." Is there a word for the more general class, narrower than "palindrome?"