Short Answer : 1
Explanation :
Considering the factors of 1290 are ( 1,2,35,6,10,15,30,43,86,129,215,258,430,645, and 1290) & knowing that a perfect square is a number that is multiplied by the same number to get your product . Your answer is 1 , none of the factors has a square root except 1 (1x1 = 1)
Even with such a large number it’s shocking there is no perfect square that is a factor other than 1 .