LXVI
LXVI is the Roman numeral for the number 66. It is formed by the symbols L (50), X (10), V (5), and I (1) arranged as LXVI, which adds up to 50 + 10 + 5 + 1 = 66. This representation uses additive notation, and does not employ subtractive forms such as IV or XL in this order.
In usage, LXVI appears in contexts that require Roman numerals to indicate a count or a year.
Beyond its basic value, the number 66 has mathematical properties that are sometimes noted in numeric contexts.