For example, the square of 2 is 4, the square of 3 is 9, the cube of 2 is 8 and the cube of 3 is 27;

Then reverse operation, the root of 4 is 2 (the root here is open twice by default), that is, 4 is the square of 2, and the root of 9 is 3.

8 Issuer is 2, 27 Issuer is 3.