Roman Numerals / 9

9 in Roman Numerals

IX

9 = IX (9, subtractive). That's IX, using one subtractive pair. 9 splits into 9 (IX), together forming IX. One below 9 is VIII (8); one above is X (10). At 2 symbols, IX is compact for 9. 9: 1 Arabic digit, 2 Roman symbols, for 9. In binary, 9 is 1001, 4 bits long for 9.