# 90 (number)

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

 List of numbers — Integers << 90 91 92 93 94 95 96 97 98 99 >>
Cardinal ninety
Ordinal90th (ninetieth)
Factorization[itex]2 \cdot 3^2 \cdot 5[itex]
Divisors 2, 3, 5, 6, 9,
15, 18, 30, 45
Roman numeralXC
Binary1011010

## In mathematics

Ninety is the sums 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 10, it is a Harshad number. But it is also a nontotient.

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 other fields

Missing image
Interstate90.png

Ninety is:

es:Noventa

• Art and Cultures
• Countries of the World (http://www.academickids.com/encyclopedia/index.php/Countries)
• Space and Astronomy