A problem with the page numbers

Algebra Level 1

A page (with 2 page numbers, front and back) has been torn out of a magazine. The sum of the page numbers on the remaining pages is 525. What is the sum of the page numbers on the page torn out?

Details and Assumptions:

Each page of the magazine is numbered on both its front and back sides.
The numbering begins with 1 on the front of the first page and proceeds consecutively in ascending order. The "remaining pages" are the pages before and/or after the page torn out.