How do you simplify the square root of 180 and how do you know that it is in the simplest form?

You list all the factors for the # under the square root (sr) and look for the largest one that is the square of a while #
180 = 2×90, 3×60, 4×45, 5×36, 6×30, 9×20, 10×18
The largest factor (besides 180) is:
90>60>45>36>30
The first 3 have no whole # as the square root, but 36 does. Since 5 has no root but 36 does (6), it can be simplified to: 6sr5