I have read your opinion. It is true what you said . Now I understand how to do this better. Thank you.

I approached the problem in a similar way (without needing to use cmath header), but I took care of the edge cases for which
n < 4 , by returning false , and for n>=4 i iterate from i=2 until i< n/2 , so I avoide having a hard coded number like 1000