39

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← 38 40 → 39
← 30 31 32 33 34 35 36 37 38 39 → List of numbers — Integers 0 10 20 30 40 50 60 70 80 90 →
Cardinal	thirty-nine
Ordinal	39th (thirty-ninth)
Factorization
Divisors	1, 3, 13, 39
Roman numeral	XXXIX
Binary	1001112
Octal	478
Duodecimal	3312
Hexadecimal	2716

39 (thirty-nine) is the natural number following 38 and preceding 40.

In mathematics

39 is the 12th distinct semiprime and the 4th in the {3.q} family. It is the last member of the third distinct biprime pair (38,39).

Thirty-nine is the sum of five consecutive primes (3 + 5 + 7 + 11 + 13) and the sum of the first three powers of 3 (3¹ + 3² + 3³). Given 39, the Mertens function returns 0.

39 is the smallest integer which has three partitions into three parts which all give the same product when multiplied: {25, 8, 6}, {24, 10, 5}, {20, 15, 4}.

39 has an aliquot sum of 17 which is itself a prime. 39 is the 4th member of the 17-aliquot tree

The thirteenth Perrin number is 39, which comes after 17, 22, 29 (it is the sum of the first two mentioned).

Since the greatest prime factor of 39² + 1 = 1522 is 761, which is obviously more than 39 twice, 39 is a Størmer number.

According to David Wells in The Penguin Dictionary of Curious and Interesting Numbers, 39 is the smallest mathematically uninteresting number. The book claims that it is also the first number that is simultaneously both interesting and uninteresting, thereby avoiding the paradox.

In science

• The atomic number of yttrium

Astronomy

• Messier object Open Cluster M39, a magnitude 5.5 open cluster in the constellation Cygnus
• The New General Catalogue object NGC 39, a spiral galaxy in the constellation Andromeda
• The Saros number of the
  • solar eclipse series which began on -1718 May 26 and ended on -438 July 3. The duration of Saros series 39 was 1280.1 years, and it contained 72 solar eclipses.
  • lunar eclipse series which began on -1380 March 26 and ended on -82 May 14. The duration of Saros series 39 was 1298.1 years, and it contained 73 lunar eclipses.

In religion

• The number of the 39 categories of activity prohibited on Shabbat according to Halakha
• The number of mentions of work or labor in the Torah
• The actual number of lashes given by the Sanhedrin to a person meted the punishment of 40 lashes
• The number of books in the Old Testament according to Protestant canon
• The number of statements on Anglican Church doctrine, Thirty-Nine Articles

In other fields

Arts and entertainment

• In the title of the John Buchan novel and subsequent films (one by Alfred Hitchcock), The Thirty-Nine Steps
• The age American comedian Jack Benny claimed to be for more than 40 years
• "39" is a song by The Cure on their album "Bloodflowers"
• "'39" is a track on Queen's album A Night At the Opera. If the tracks on Queen's original studio albums are numbered in sequential order starting with their first, "'39" does in fact fall in the thirty-ninth position
• The retired jersey number of former baseball player Roy Campanella
• The series "The 39 Clues" evolves around a series of 39 clues.

History

• The number of signers to the United States Constitution, out of 55 members of the Philadelphia Convention delegates
• The traditional number of times citizens of Ancient Rome hit their slaves when beating them, referred to as "Forty save one"
• The duration, in nanoseconds, of the nuclear reaction in the largest nuclear explosion ever performed (Tsar bomb)
• The number of Scud missiles which Iraq fired at Israel during the Gulf War in 1991

Other

• The code for international direct-dialed phone calls to Italy
• I-39 is the designation for a US interstate highway from Normal, Illinois to Wausau, Wisconsin. I-39 is the 39th shortest of the primary "two digit" Interstates.
• Japanese Internet chat slang for "thank you" when written with numbers (3=san 9=kyu)
• Pier 39 in San Francisco
• The number of the French department Jura

At age 39

• Apollo 11 commander Neil Armstrong became the 1st person to set foot on the moon
• Charles Goodyear led the way to the effective use of rubber
• Jimmy Connors reached the U.S. Open semifinals
• Malcolm X was assassinated
• Martin Luther King Jr. was assassinated
• Amelia Earhart went missing; she was declared dead 2 years later in 1937

Historical years

39 A.D., 39 B.C., 1939, 2039, etc.