130 (one hundred
ndthirty) 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
129 and preceding
131.
In mathematics
130 is a
sphenic number. It is a
noncototient
In number theory, a noncototient is a positive integer that cannot be expressed as the difference between a positive integer and the number of coprime integers below it. That is, , where stands for Euler's totient function
In number theory ...
since there is no answer to the equation ''x'' -
φ(''x'') = 130.
130 is the only integer that is the sum of the squares of its first four divisors, including 1: 1
2 + 2
2 + 5
2 + 10
2 = 130.
130 is the largest number that cannot be written as the sum of four
hexagonal numbers.
130 equals both 2
7 + 2 and 5
3 + 5 and is therefore a ''doubly strictly '' number.
In other fields
* A
130-30 fund or a ratio up to 150/50 is a type of collective investment vehicle
References
{{DEFAULTSORT:130 (Number)
Integers