Multiples of 10 are: 10, 20, 30, 40, 50, ... and so on.
Only one of them: 20 falls between 15 and 28.
Other conditions are also true for 20 - it has a factor that is an even number (all its even factors are: 2, 4, 10, 20) and it has a factor that is an odd number (all its odd factors are: 1, 5).