73 (number)

← 72 74 → 73
← 70 71 72 73 74 75 76 77 78 79 → List of numbers — Integers 0 10 20 30 40 50 60 70 80 90 →
Cardinal	seventy-three
Ordinal	73rd (seventy-third)
Factorization	prime
Prime	21st
Divisors	1, 73
Roman numeral	LXXIII
Binary	10010012
Octal	1118
Duodecimal	6112
Hexadecimal	4916

73 (seventy-three) is the natural number following 72 and preceding 74. In English, it is the smallest integer with twelve letters in its spelled out name.

In mathematics

• Seventy-three is the 21st prime number. The previous is seventy-one, with which it comprises the 8th twin prime. It is also a permutable prime with thirty-seven. 73 is a star number.
• 73 is the largest minimal Primitive root in the first 100000 primes. In other words, if p is one of the first 100000 primes, then at least one of the primes 3, 5, 7, 11, 13, 17, ..., 73 is a primitive root modulo p.
• 73 is the smallest prime congruent to 1 modulo 24.
• The mirror of 73, the 21st prime number, 37, is the 12th prime number. The number 21 includes factors 7 and 3. Seventy-three in binary, 1001001, is a palindrome. In addition, of the 7 binary digits representing 73, there are 3 ones. Also, 37+12=49 (seven squared) and 73+21=94=47*2, 47+2 also being equal to seven squared. Additionally, both 73 and its mirror, 37, are sexy primes twice over, as 31, 43, 67 and 79 are all prime numbers.
• The square root of 73 is 8.544. The sum of which (8+5+4+4) equals the product of 7 and 3; 21.
• Every positive integer can be written as the sum of 73 or fewer sixth powers (see Waring's problem).
• In base 5, the smallest prime with a composite sum of digits is 73.
• 73 is the only prime repunit in base 8 (111₈)
• 73 is the smallest factor of the first composite generalized Fermat number in base 10 (10⁴+1 = 10,001 = 73*137)

In science

• The atomic number of tantalum

In astronomy,

Messier object M73, a magnitude 9.0 apparent open cluster in the constellation Aquarius

The New General Catalogue object NGC 73, a barred spiral galaxy in the constellation Cetus

The Saros number of the solar eclipse series which began on 717 BC July and ended on 582 September. The duration of Saros series 73 was 1298.1 years, and it contained 73 solar eclipses.

The number of seconds it took for the OV-099 shuttle to explode after launch.

• 73 is the length of the Arecibo message, sent to space in search for extraterrestrial intelligence.

In popular culture

Dr. Sheldon Cooper in The Big Bang Theory, played by actor Jim Parsons, said "The best number is 73. Why? 73 is the 21st prime number. Its mirror (37) is the 12th and its mirror (21) is the product of multiplying, 7 and 3. ... In binary, 73 is a palindrome, 1001001 which backwards is 1001001."

Sheldon's roommate, Leonard Hofstadter, then quips that "73 is the Chuck Norris of numbers," to which Sheldon replies "Chuck Norris wishes. [...] All Chuck Norris backwards gets you is Sirron Kcuhc!"[1]

Sheldon's devotion to the number is illustrated in several further episodes, when he wears a t-shirt emblazoned with it, for example in The Roommate Transmogrification.

In other fields

Seventy-three is also:

• The total number of books in the Holy Bible in the Catholic version if the Book of Lamentations is counted as a book separate from the Book of Jeremiah.
• The designation of USA Interstate 73, a freeway in North Carolina.
• The registry of the U.S. Navy's nuclear aircraft carrier USS George Washington (CVN-73), named after U.S. President George Washington.
• The year AD 73, 73 BC, or 1973.
• Amateur radio operators often use the number 73 as an abbreviation for "best regards", typically when ending a QSO (a conversation with another ham). [2] In Morse code, 73 is a palindrome (--··· ···--).
• 73 (also known as 73 Amateur Radio Today), was an amateur radio magazine published from 1960 to 2003.
• international amateur radio code, meaning "best regards"
• Each of the five seasons of the Discordian calendar has 73 days.
• No. 73 was name of a 1980s children's television programme in the United Kingdom. It ran from 1982-1988 and starred Sandi Toksvig
• The Blues Image song "Ride Captain Ride" (1970) begins with "73 men sailed out on the San Francisco Bay"
• Singer Johnny Mathis has had 73 charted albums on Billboard Top 200 Charts
• Pizza 73 is a Canadian pizza chain with 51 stores
• Game show Match Game '73 in 1973
• The Felony Squad aired on ABC from '66 - '69 for 73 episodes
• The TV show Hope & Faith aired on ABC, 2003 - 2006 for 73 episodes
• Fender Rhodes Stage 73 Piano
• Sonnet 73 by William Shakespeare
• PT-73, the PT boat on TV's McHale's Navy
• 73 is the current area of resistance to the downside of the iTraxx Europe Series 9 5y credit index. The number has taken on almost mythical status amongst the denizens of the financial community in London
• The number of the French department Savoie
• On a CB radio, 10-73 means "speed trap at..."
• The favorite number of The Big Bang Theory's character Sheldon Cooper

In sports

• In international curling competitions, each side is given 73 minutes to complete all of its throws.
• The car number of former NASCAR driver Johnny Beauchamp.
• The best-known car number of retired NASCAR driver Phil Barkdoll.
• In baseball, the single-season home run record set by Barry Bonds in 2001.
• In basketball, the number of games the Philadelphia 76ers lost in the 1972-73 season (9-73), the most losses in NBA history.
• University of Texas football player Jonathan Scott wore #73
• NFL: New England Patriots John Hannah's retired #73
• NFL: New York Jets Joe Klecko's retired #73
• NFL: In the 1940 NFL championship game, the Bears beat the Redskins 73-0, the largest score ever in an NFL game. (The Redskins won their previous regular season game, 7-3). For more details, see Wikipedia article 1940 NFL Championship Game