90 (number)
Category:Integers\n
90 is the
natural number preceded by
89 and followed by
91.
In mathematics
\nNinety is the sums of the squares of the integers 2 to 6, as well as a
highly composite number. 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
\nNinety is:\n*The atomic number of
thorium, an actinide.\n*The designation of
American Interstate 90, a freeway that runs from
Washington to
Massachusetts.\n*The
code for international direct dial phone calls to
Turkey.\n* The year AD
90,
90 BC, or
1990.
\n\n\n
