222 is both a three-digit integer with several elementary mathematical properties and a label used for historical years in different calendars. As a numeral it is a repdigit made of three identical digits and reads the same forward and backward in base 10. As a year it most commonly denotes AD 222 in the Julian calendar, a year associated with political change in the Roman Empire and military activity in East Asia during the Three Kingdoms period.
Mathematical characteristics
In arithmetic, 222 is an even composite number with prime factorization 2 × 3 × 37, which makes it a sphenic number (the product of three distinct primes). Its positive divisors are 1, 2, 3, 6, 37, 74, 111 and 222. The sum of its proper divisors is 234, which exceeds 222, so it is classified as an abundant number. It is divisible by the sum of its decimal digits (2 + 2 + 2 = 6), so 222 is a Harshad number. In common numeric systems 222 is represented as 11011110 in binary, 336 in octal and DE in hexadecimal, and in Roman numerals it is written CCXXII.
Year AD 222: historical context and events
The designation AD 222 refers to a year in the early 3rd century. In the Roman Empire the year is remembered for the violent end of the reign of the emperor often called Elagabalus and for the succession of Alexander Severus, who assumed the imperial title with the support of the Praetorian Guard and the imperial administration. These events were part of the broader turbulence of the Severan period and imperial politics of the era. In East Asia, the post-Han Three Kingdoms environment remained militarized: campaigns and clashes between the states of Wei, Shu Han and Eastern Wu continued, and operations led by Liu Bei against Eastern Wu in this period culminated in decisive engagements in the campaigns of 222–223.
Other uses and references
The sequence 222 appears in many practical identifiers and cultural contexts. The international telephone country code +222 is assigned to Mauritania. In firearms and shooting sports, ".222" commonly refers to the .222 Remington cartridge, a small-caliber round developed for varmint hunting and target use. In science, the label 222 is associated with naturally occurring isotopes such as radon-222, a radioactive decay product that occurs in uranium decay chains and is notable for its role in environmental radioactivity. Repeating digit patterns like 222 are also used informally in popular culture, designators, model numbers and as mnemonic or symbolic motifs in various traditions; interpretations vary and are culturally dependent.
As a concise label, 222 thus functions on several levels: as a numeric object with clear factorization and representational forms; as a chronological marker for historical events; and as a recognizable string used in communications codes, product names and cultural references.