A Friedman number, named after Stetson University mathematician Erich Friedman, is a number that can be calculated using its own digits, such as 736 = 3⁶ + 7 or 3281 = (3⁸ + 1) / 2.

A “nice” Friedman number is one in which the digits are used in order, such as 3685 = (3⁶ + 8) × 5 or 3972 = 3 + (9 × 7)².

Might this be done in other number systems? In a sense all Roman numerals are automatically Friedman numbers, but there are some interesting nontrivial examples as well:

XVIII = IV × II + X

LXXXIII = IX^X×X/L + II

And it turns out that “nice” examples are possible here too, in which a number’s letters are used in order:

LXXVI = L / X × XV + I

LXXXIV = LX / X × XIV

Is there more? Friedman has begun looking for examples in Mayan numerals — see his website.