Solution

154607

First name
Isabelle Slater
School
Maidstone Grammar School for Girls
Country
Age
15

The number in the first row is '142857'.

The complete square is displayed as follows:

1 4 2 8 5 7
2 8 5 7 1 4
4 2 8 5 7 1
5 7 1 4 2 8
7 1 4 2 8 5
8 5 7 1 4 2