[math-fun] Hereditary Representation with 2's

Hello Math-Fun, which integers -- using only the digit '2' -- have an hereditary representation using only 2's? (no 1's allowed)? Integer 2 is a hit, of course, but what about 22, 222, 2222, 222222 etc.? http://mathworld.wolfram.com/HereditaryRepresentation.html Best, É.