Alphabetical priority of the isopropyl group
The iso prefix is included in the alphabetic order. 

For eg:- The compound Thymol has the following IUPAC name :- 2-Isopropyl-5-methylphenol and not 5-methyl-2-Isopropylphenol.

Therefore the name of your compound should be 4-isopropyl-2,3,3-trimethylheptane.