72 (number)

72 (seventy-two) is the natural number following 71 and preceding 73. It is half a gross or 6 dozen (i.e., 60 in duodecimal).

In mathematics

Seventy-two is the sum of four consecutive primes (13 + 17 + 19 + 23), as well as the sum of six consecutive primes (5 + 7 + 11 + 13 + 17 + 19). The product of 8 and 9, 72 is a pronic number.

The sum of Euler's totient function φ(x) over the first fifteen integers is 72. There are 17 solutions to the equation φ(x) = 72, more than any integer below 72, making it a highly totient number.

72 is the smallest number whose fifth power is the sum of five smaller fifth powers: 19⁵ + 43⁵ + 46⁵ + 47⁵ + 67⁵ = 72⁵.

The sum of the eighth row of Lozanić's triangle is 72.

In a plane, the exterior angles of a regular pentagon measure 72 degrees each.

In base 10, the number 72 is a Harshad number.

In science

• The atomic number of hafnium
• In degrees Fahrenheit considered to be room temperature.
• The average number of heartbeats per minute for a resting adult.
• Percentage of water of which the human body is composed.
• The life duration of the ovule is 72 hours.
• The axis of the earth moves one degree every 72 years compared to stars and to the vault of heaven.

In astronomy

• The 72 Paranatellons, extra-zodiacal constellations that rise and set simultaneously with zodiacal constellations.
• Messier object M72, a magnitude 10.0 globular cluster in the constellation Aquarius.
• The New General Catalogue object NGC 72, a magnitude 13.5 barred spiral galaxy in the constellation Andromeda.
• The Saros number of the solar eclipse series which began on -727 August 16 and ended on 752 January. The duration of Saros series 72 was 1478.1 years, and it contained 83 solar eclipses.
• The Saros number of the lunar eclipse series which began on -407 June 5 and ended on 891 July. The duration of Saros series 72 was 1298.1 years, and it contained 73 lunar eclipses.
• The precession of equinoxes traces out a pair of cones joined at their apices in a cycle of approximately 26,000 years, that is 1 degree every 72 years (approximation to the nearmost integer).

In religion

• The number of languages spoken at the Tower of Babylon, according to later tradition.
• The conventional number of scholars translating the Septuagint, according to the legendary account in the "Letter of Aristeas".
• The conventional number of disciples sent forth by Jesus in Luke 10 in some manuscripts (seventy in others).
• The number of names of God, according to Kabbalah (see names of God in Judaism).
• The Shemhamphorasch related to the number of the names of God.
• The total number of books in the Holy Bible in the Catholic version if the Book of Lamentations is considered part of the Book of Jeremiah.
• The current distribution of the Book of Revelation is 22 chapters, adopted since the 13th century, but the oldest known division of the text is that of the Greek commentator Andrew of Cesary (6th century) in 72 chapters.
• The number of warriors on the Muslim side at the Battle of Badr.
• The number of people martyred along with Imam Hussain at the Battle of Karbala.
• The number of soldiers who will fight alongside Imam Mahdi against the Dajjal, according to Islamic ahadith are 313 not 72.
• The 72 old men of the synagogue, according to the Zohar.
• The number of houri each Muslim martyr (or every Muslim male, according to some ahadith) shall receive as companions in Paradise.
• The degrees of the Jacob's Ladder were to the number of 72, according to the Zohar.
• The 72 disciples of Confucius who mastered his teachings (also given as 77).
• Mahavira, the twenty-fourth and last tirthankara of Jainism, is said to have attained nirvana after his physical death at the age of 72.
• Thoth, in an Egyptian creation myth, wins a 72nd of each day of the year from the Moon in a game of draughts, as a favour to Nut, the Sky Goddess. He uses these portions to make the five intercalary days on which the remaining Gods and Goddesses are born.^[1]
• The good god Osiris was enclosed in a coffin by 72 evil disciples and accomplices of Set.^[2]
• At the age of the puberty, the young Parsee received the investiture of the sacred cord Kucti made of 72 linens in symbol of the community.
• In Cao Đài, the number of planets between hell and heaven.
• There are 72 stupas which comprise Borobudur, the world’s largest Buddhist temple.
• 72 major temples have been found at Angkor, seat of the ancient Khmer Empire.
• In Islam, 72 is the number of sects or denominations that are doomed to Hell, according to Hadith (Sayings of prophet Muhammad).^[3][4]

In other fields

Seventy-two is also:

• The number of hours in 3 days.
• In dpi, the default screen resolution for an image or graphic on an Apple Macintosh screen.
• In typography, point sizes are measured in 1/72 of an inch, 72-point characters are 1 inch tall.
• The number of the French department Sarthe.
• The designation of USA Interstate 72, a freeway that runs from Missouri to Illinois, East <> West.
• Municipal Okrug 72, a municipal okrug of Frunzensky District of Saint Petersburg, Russia
• The registry of the U.S. Navy's nuclear aircraft carrier USS Abraham Lincoln (CVN-72), named after U.S. President Abraham Lincoln.
• The designation of the Soviet T-72 tank.
• In the movie The Red Violin, the lot number of the Bussotti red violin at the DuVal auction house.
• The year AD 72, 72 BC, 1972, or any other year ending with "72".
• The Rule of 72 in finance.
• Book: 72 Hour Hold by Bebe Moore Campbell (referring to an involuntary psychiatric hold)
• CD: Seventy Two & Sunny by Uncle Kracker
• Jill Clayburgh and LeVar Burton starred in Firestorm: 72 Hours in Oakland (1993)
• Alternative music band The Delta 72
• New York's Dakota Apartments and Strawberry Fields are by 72nd St. and Central Park West
• The Persian classical santur, a hammered dulcimer, has 72 strings in 24 triple-stringed courses.
• The number of episodes in the original airing of Futurama.
• The Turin Brakes song, also known as Emergency 72
• The number of members in National Senate of Argentina.
• A Civil Air Patrol unit in Laramie, WY, RMR-WY-072.
• There are 72 demons and other spirits in the goetia The Lesser Key of Solomon.
• A form of radio shorthand that roughly translates as meaning "Best wishes" in the QRP (low power) community
• A common limit for characters per line in computing
• 72 equal temperament is a tuning used in Byzantine music and by some modern composers.

In sports and games

• The usual par for an 18 hole golf course, especially those in tournament play.
• The number of victories the Chicago Bulls achieved during the 1995-96 NBA season, which is the National Basketball Association record.
• The number of spaces in a game of Parcheesi, from start space to "home."

Footnotes

External links

• Go Figure: What can 72 tell us about life, BBC News, 20 July 2011