Find the Squarish Root
Python3, 49 47 bytes

def f(x):
 l=x**.5//1
 while x%l:l-=1
 return l


Explanation


l=x**.5//1 &rarr; Assign l the largest integer less than equal to the square root of x
while x%l:l-=1 &rarr; While l does not evenly divide x, decrement l.


Edits


Mention Python3, not Python2
Use ...//1 to save two bytes.  (Decimals are okay!  Thanks @Rod)