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For the video game company 'Ninty' see Nintendo. 90 (ninety) is the natural number preceded by 89 and followed by 91.
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. 90 is a pronic number. And because 90 is divisible by the sum of its digits in base-ten, it is a Harshad 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. In astronomy In other fields Ninety is: | ||||||||
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