The factors of 525 are 1, 3, 5, 7, 15, 21, 25, 35, 75, 105, 175, and 525.
All of those numbers go into 525 evenly.
The factors of 24 are 1, 2, 3, 4, 6, 8, 12, and 24.
All of those numbers go into 24 evenly.
The common factors of 525 and 24 are 1, and 3 .
Those are the numbers that go into both 525 and 24 evenly.