Because the serial numbers of the two products are the same, we can find this number first.

Because 525 = 5 * 5 * 3 * 7,700 = 5 * 5 * 4 * 7,

And the first time must be a single digit 1, so 525 = 25 * 2 1, 700 = 25 * 28,

So the original numbers are 24 and 25, that is, the product is 25*24=600.