Remember that the factors of an odd number are all odd.

For example the factors of 15 are: 1, 3, 5 and 15.

If we look at a bigger number like 2,469 the factors are: 1, 3, 823, 2469.

And just to prove the point, for a huge number like 24,648,021 the factors are: 1, 3, 9, 53, 159, 477, 51673, 155019, 465057, 2738669, 8216007, 24648021.

Phew!