**Solution**: 7917510

**Logic**

All letters whose position in the alphabet is below 10, are being represented by position number. All letters whose position is 10 or more, are being represented by their position less ten.

So

G is 7

R is 18-9=9

A is 1

P is 16-9=7

E is 5

S is 19-9=10

so..... 791751