70 (number)

Look up seventy in Wiktionary, the free dictionary.

70 (seventy) is the natural number following 69 and preceding 71.

In mathematics

70 is:

• a sphenic number because it factors as 3 distinct primes.^[1]
• a Pell number and a generalized heptagonal number, one of only two numbers to be both.^[2]
• the seventh pentagonal number.^[3]
• the fourth triskaidecagonal number.^[4]
• the fifth pentatope number.^[5]
• the smallest weird number, a natural number that is abundant but not semiperfect.^[6]
• a palindromic number in bases 9 (77₉), 13 (55₁₃) and 34 (22₃₄).
• a Harshad number in bases 6, 8, 9, 10, 11, 13, 14, 15 and 16.
• an Erdős–Woods number, since it is possible to find sequences of 70 consecutive integers such that each inner member shares a factor with either the first or the last member.^[7]

The sum of the first 24 squares starting from 1 is 70². This relates 70 to the Leech lattice and thus string theory.

In science

• 70 is the atomic number of ytterbium, a lanthanide

Astronomy

• Messier object M70, a magnitude 9.0 globular cluster in the constellation Sagittarius
• The New General Catalogue object NGC 70, a magnitude 13.4 spiral galaxy in the constellation Andromeda
• The Saros number of the solar eclipse series which began on 821 BC September 5 and ended on 676 February. The duration of Saros series 70 was 1496.5 years, and it contained 84 solar eclipses. Further, the Saros number of the lunar eclipse series which began on 519 BC June 13 and ended on 761 July. The duration of Saros series 70 was 1280.1 years, and it contained 72 lunar eclipses.

In religion

• In Jewish tradition:
  • Seventy souls went down to Egypt to begin the Hebrews' Egyptian exile (Genesis 46:27).
  • There is a core of 70 nations and 70 world languages, paralleling the 70 names in the Table of Nations.
  • There were 70 men in the Great Sanhedrin, the Supreme Court of ancient Israel. (Sanhedrin 1:4.)
  • According to the Jewish Aggada, there are 70 perspectives ("faces") to the Torah (Numbers Rabbah 13:15).
  • Seventy elders were assembled by Moses on God's command in the desert (Numbers 11:16-30).
  • Psalm 90:10 allots three score and ten (70 years) for a man's life, and the Mishnah attributes that age to "strength" (Avot 5:32), as one who survives that age is described by the verse as "the strong".
  • Ptolemy II Philadelphus ordered 72 Jewish elders to translate the Torah into Greek; the result was the Septuagint (from the Latin for "seventy"). The Roman numeral seventy, LXX, is the scholarly symbol for the Septuagint.
• In Christianity:
  • In Matthew 18:21-22, Jesus tells Peter to forgive people seventy times seven times.
  • In Luke 10:1-24, Jesus appoints Seventy Disciples and sends them out in pairs to preach the Gospel.
• Seventy is a priesthood office in the Latter Day Saint religion.
• In Islamic history and in Islamic interpretation the number 70 or 72 is most often and generally hyperbole for an infinite amount:
  • There are 70 dead among the Prophet Muhammad's adversaries during the Battle of Badr.
  • 70 of the Prophet Muhammad's followers are martyred at the Battle of Uhud.
  • In Shia Islam, there are 70 martyrs among Imam Hussein's followers during the tragedy of Karbala.

In law

• In certain cases, copyrights expire after 70 years.

In sports

• NASCAR driver J. D. McDuffie was known for driving car #70.
• In Olympic archery, the targets are 70 meters from the archers.
• In college football, West Virginia Mountaineers scored 70 points against Clemson Tigers in the 2012 Orange Bowl, setting the record as the most points ever scored by one side in the history of all bowl games.

In other fields

• USA Interstate 70 goes from Utah to Maryland.
• Municipal Okrug 70 was the name of Kolomyagi Municipal Okrug of Primorsky District of Saint Petersburg, Russia until February 2011.
• 70 miles per hour is a common speed limit for freeways in many American states, primarily in the central United States (in the Eastern U.S. the speed limit is generally 65, in the Western U.S. it is 75).
• 70 miles per hour is the national speed limit in the United Kingdom for cars and motorcycles on the best grades of road.^[8]
• 70 years of marriage is marked by a platinum wedding anniversary.
• 70 is the hull number of the U.S. Navy's nuclear aircraft carrier USS Carl Vinson (CVN-70), named after U.S. Representative Carl Vinson.
• The French department Haute-Saône is number 70.
• As a year, "70" may refer to 70 BC, AD 70, or 1970.
• The number 70 is frequently referenced by the musical duo Boards of Canada: they have songs titled "Sixtyten" (Music Has the Right to Children, 1998) and "The Smallest Weird Number" (Geogaddi, 2002), and their record label is named Music70.
• In the Far Eastern culture of China, Japan, Korea, etc., 70 years old is called the Rare Age of the Olden Times (古稀 Guxi in Chinese, 古稀 Koki in Japanese, 고희 Gohui in Korean, etc.), as written in one of Du Fu’s poems.^[9]

Number name

Several languages, especially ones with vigesimal number systems, do not have a specific word for 70: for example, French soixante-dix "sixty-ten"; Danish halvfjerds, short for halvfjerdsindstyve "three and a half score". (For French, this is true only in France; other French-speaking regions such as Belgium, Switzerland, Aosta Valley and Jersey use septante.^[10])

Notes