678

678 is the natural number that follows 677 and precedes 679. It is even and composite, with prime factorization 678 = 2 × 3 × 113. Its positive divisors are 1, 2, 3, 6, 113, 226, 339, and 678. The digit sum is 21, so the number is divisible by 3 (and by 6, since it is even).

In other bases, 678 appears as 1010100110 in binary, 1246 in octal, and 2A6 in hexadecimal. In Roman numerals it is written as DCLXXVIII.

As a year, 678 CE falls within the late 7th century and is associated with the Byzantine–Arab conflicts of the era. Notably, it marks the end of the first Arab siege of Constantinople, with Byzantine defenders under Emperor Constantine IV repelling the assault.

In contemporary usage, 678 functions as an area code within the North American Numbering Plan, used in parts of the Atlanta metropolitan region in Georgia, United States. The number also appears in various symbolic or cataloging contexts as a finite integer in mathematical, historical, or logistical discussions.