Burt Kaliski Jr. (@modulomathy) 3/31/12 1:21 PM #math trivia for #March31: #91 is XCI in Roman numerals. What other numbers this year only use the Roman powers of 10 (I, X and C)? A Roman numeral can have as many as three consecutive Is, Xs and Cs, so a number in the 0s, 100s, 200s … Continue reading