90 (NUMBER)

'90' ('ninety') is the natural number preceded by 89 and followed by 91.

Cardinal	90 ninety
Ordinal	90th ninetieth
Factorization	$2\; cdot\; 3^2\; cdot\; 5$
Divisors	1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90
Roman numeral	XC
Roman numeral (Unicode)	XC, xc
Binary	1011010
Octal	132
Duodecimal	76
Hexadecimal	5A
Hebrew	צ (Tsadi)

Contents

In mathematics

In astronomy

In other fields

In sports

References

In mathematics

90 is the sum of the squares of the integers 2 to 6. Because 90 is the sum of its unitary divisors (excluding itself), it is a unitary perfect number, and because it is equal to the sum of a subset of its divisors, it is a semiperfect number. 90 is a pronic number. But it is also a nontotient. It is a Perrin number, preceded in the sequence by 39, 51, 68.
In normal space, the interior angles of a square measure 90 degrees each. Also, in a right triangle, the angle opposing the hypotenuse measures 90 degrees, with the other two angles adding up to 90 for a total of 180 degrees. Thus, an angle measuring 90 degrees is called a right angle.^[1]
90 is divisible by the sum of its base 10 digits, thus it is a Harshad number.

In astronomy

★ Messier object M90, a magnitude 11.0 spiral galaxy in the constellation Virgo

★ The New General Catalogue object NGC 90, a barred spiral galaxy in the constellation Andromeda

★ The Saros number of the solar eclipse series which began on 134 BC September 28 and ended on 1345 March 4. The duration of Saros series 90 was 1478.4 years, and it contained 83 solar eclipses.

★ The Saros number of the lunar eclipse series which began on 150 June 27 and ended on 1430 August 4. The duration of Saros series 90 was 1280.1 years, and it contained 72 lunar eclipses.

In other fields

'Ninety' is:

★ The year AD 90, 90 BC, or 1990.

★ The 1890’s were known as the Gay Nineties

★ Abbott and Costello "The Naughty Nineties" film (1945)

★ The atomic number of thorium, an actinide.

★ The atomic weight of an isotope of strontium, a by-product of nuclear reactions including fallout. It contaminates milk.

★ The latitude of the North Pole and the South Pole.

★ The designation of United States Interstate 90, a freeway that runs from Washington to Massachusetts.

★ The code for international direct dial phone calls to Turkey.

★ The ISBN Group Identifier for books published in the Netherlands.

★ The Soviet T-90 tank is the most modern in the Russian arsenal.

★ The number of minutes in a football match.

★ In the song "My Grandfather's Clock" by Henry Clay Work, the number of years the clock stood on the floor.

★ Was the percent chance that the employees of Colonies.com had of getting paid on Monday the 11th of June; it turns out it should have been 0%.

★ The number of a psalm credited to Moses; the ninety-first psalm is also likely his work as well.

★ 90 minute cassette tapes

★ "90 Miles An Hour (Down A Dead End Street" by Hank Snow

★ Mission 90 Days film (2007)

★ "Bob Hope: The First 90 Years" TV special aired on NBC on May 14, 1993)

★ Joe 90, a 1968 U.K. TV series, set in 2012

★ [Power 90] weight loss and body transformation program

★ [Ultra 90], weight loss program

★ Playhouse 90, a 90-minute long dramatic CBS TV series from 1956-61

★ Cuba is 90 miles off the Florida coast

★ Gloria Estefan "90 Millas" CD (90 miles)

★ Eli Wallach starred in "The Holiday" in 2006 at 90

★ Nokia E90 Communicator

★ David Hasselhoff and "Knight Rider" aired for 90 episodes from 1982 - 1986

★ by Don Piper

In sports

★ Nike Total 90 Apparel is a brand name of apparel and sports equipment from equipment bags to goalkeeper gloves

★ Major League baseball bases are 90 feet away in distance

★ The car number most associated by former NASCAR team owner Junie Donlavey

References

1. Friedman, Erich. What's Special About This Number?