Answer:
Irrational number
Explanation:
A number which can be written in the form of a fraction
, is a rational number.
Examples :

In 1.41414141..... (41) is the repeating numbers after decimal. Therefore, it's a rational number.
Irrational numbers can't be written in the form of
.
Examples : π, √3, 1.41456......
Given number in the question is 6.56556555....
In this number numbers after decimal are not repeating.
Therefore, given number is irrational.