123 (number)

123 (one hundred [and] twenty-three) is the natural number following 122 and preceding 124.

In mathematics

 * 123 is a Lucas number. It is the eleventh member of the Mian–Chowla sequence.
 * Along with 6, 123 is one of only two positive integers that is simultaneously two more than a perfect square and two less than a perfect cube (123 = 112 + 2 = 53 - 2).
 * 123 is the first whole number containing numbers from 1 to 3.

In religion
The Book of Numbers says that Aaron died at the age of 123.

In numerology, the sequence of 123 is associated with progress and the Holy Trinity, so it may be referred to as the Trinity of Progress or Triad of Progress.

In telephony

 * The emergency telephone number in Colombia
 * The telephone number of the speaking clock for the correct time in the United Kingdom
 * The electricity (PLN) emergency telephone number in Indonesia
 * The medical emergency telephone number in Egypt
 * The Notation for national and international telephone numbers Recommendation ITU-T Recommendation E.123 defines a standard way to write telephone numbers, e-mail addresses, and web addresses

In other fields
123 is also:
 * 123 (film), a 2002 Indian film
 * 123 (interbank network), shared cash network in Egypt
 * 123 (New Jersey bus)
 * "1-2-3", 1965 song written and recorded by Len Barry
 * The atomic number of the yet-to-be-discovered element unbitrium