70 (number)

70 is a composite number, an Erdős–Woods number^[1], a Pell number, a central binomial coefficient^[2], and a primitive abundant number. 70 is the smallest weird number, which is a natural number that is abundant but not semiperfect.^[3]

70 is also part of the only nontrivial solution pair to the cannonball problem, along with 24.

• In Jewish tradition, 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 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 Muhammad's adversaries during the Battle of Badr.
  • 70 of Muhammad's followers are martyred at the Battle of Uhud.
  • In Shia Islam, there are 70 martyrs among Imam Hussein's followers during the Battle of Karbala.

• In some traditions, 70 years of marriage is marked by a platinum wedding anniversary.
• Under Social Security (United States), the age at which a person can receive the maximum retirement benefits (and may do so and continue working without reduction of benefits).

Look up seventy in Wiktionary, the free dictionary.

Several languages, especially ones with vigesimal number systems, do not have a specific word for 70: for example, French: soixante-dix, lit. 'sixty-ten'; Danish: halvfjerds, short for halvfjerdsindstyve, 'three and a half score'. (For French, this is true only in France, Canada and Luxembourg; other French-speaking regions such as Belgium, Switzerland, Aosta Valley and Jersey use septante.)^[4]