LXXVIII

LXXVIII is the Roman numeral for the number 78. It is composed as L (50) plus XX (20) and VIII (8), yielding 50 + 20 + 8 = 78. The numeral uses additive notation rather than the more compact subtractive forms found in other numbers such as XL or IX.

Roman numerals are still used in certain contexts, and LXXVIII may appear on inscriptions, monuments, clock faces, book chapters, movie or television episode numbering, or to denote the year in historical timelines written using antiquated numerals. In modern usage, it is customary to spell out numbers below 100 or to use Arabic numerals, except in specific stylistic or traditional contexts.

78 is an even, composite number with prime factorization 2 × 3 × 13. Its proper divisors are 1, 2, 3, 6, 13, 26, and 39; the sum is 90, making 78 an abundant number. It can also be expressed as the product of 6 and 13, and it is divisible by 2, 3, 6, and 13.

Historically, a date written as 78 AD would fall within the early Roman Empire, during the reign of Emperor Vespasian. A date such as 78 BCE would occur in the late Roman Republic period. LXXVIII thus may appear when dating events in Roman-era sources or in modern discussions of Roman numerals in teaching materials.