Well, I don’t know if this is known already, so if it is, please comment the name of the theorem. If it isn’t, then someone put a comment on what it should be called. A number with all of its digits less than 2 (which means only 0 and 1) and has less than 10 digits, multiplied with a number with the same characteristics has a product reverse of that of another set of two numbers with the same digits as the first set but has its digits reversed. Example below.
111111111 x 111111101 = 12345677876543211
111111111 x 101111111 = 11234567877654321
Thanks to Kirk Bamba for this submission!