16
16 = 24 = 42
(only integer solution ab = ba)
216 - 1 = 3 * 5 * 17 * 257
1016 - 1 = 3 * 3 * 11 * 17 * 73 * 101 * 137 * 5882353
15 - 16 - 17
0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9
Mathematics Encyclopedia
Hellenica World - Scientific Library
