90 (number)

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"Ninety" redirects here. It is also often used^[1] as a name of endearment for Nintendo.

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

← 90 91 92 93 94 95 96 97 98 99 → List of numbers — Integers 0 10 20 30 40 50 60 70 80 90 →
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)

Look up ninety in
Wiktionary, the free dictionary.

1 In mathematics
2 In astronomy
3 In other fields
4 In sports
5 References

[edit] 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.^[2]

90 is divisible by the sum of its base 10 digits, thus it is a Harshad number.

[edit] 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.

[edit] In other fields

Interstate 90

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 Russian T-90 tank is the most modern in their arsenal.
The number of minutes in a football (soccer) match.
In the song "My Grandfather's Clock" by Henry Clay Work, the number of years the clock stood on the floor.
The number of Psalms credited to Moses; the ninety-first psalm is also likely his work.
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
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)
Nokia E90 Communicator
90 Minutes in Heaven: A True Story of Death and Life by Don Piper