220 (two hundred
ndtwenty) is the
natural number
In mathematics, the natural numbers are the numbers 0, 1, 2, 3, and so on, possibly excluding 0. Some start counting with 0, defining the natural numbers as the non-negative integers , while others start with 1, defining them as the positive in ...
following
219 and preceding
221.
In mathematics
It is a
composite number
A composite number is a positive integer that can be formed by multiplying two smaller positive integers. Accordingly it is a positive integer that has at least one divisor other than 1 and itself. Every positive integer is composite, prime numb ...
, with its proper divisors being 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110, making it an
amicable number with
284. Every number up to 220 may be expressed as a sum of its divisors, making 220 a
practical number.
It is the sum of four consecutive primes (47 + 53 + 59 + 61). It is the smallest even number with the property that when represented as a sum of two prime numbers (per
Goldbach's conjecture) both of the primes must be greater than or equal to 23.
There are exactly 220 different ways of
partitioning 64 = 8
2 into a sum of
square numbers.
It is a
tetrahedral number, the sum of the first ten
triangular numbers, and a dodecahedral number. If all of the diagonals of a regular
decagon are drawn, the resulting figure will have exactly 220 regions.
It is the sum of the sums of the divisors of the first 16
positive integers.
Notes
References
* Wells, D. (1987). ''
The Penguin Dictionary of Curious and Interesting Numbers'' (pp. 145 – 147). London: Penguin Group.
{{DEFAULTSORT:220 (Number)
Integers