Answer to POW #7:

There are five possible lists, which can be obtained by thinking about which of the numbers from 1 to 9 can be used in the list as single digits and which can be used as the last digit in a multi-digit number, and then eliminating possibilities. The five lists are:

2, 3, 5, 7, 89, 641
2, 3, 5, 7, 89, 461
2, 3, 5, 41, 67, 89
2, 3, 5, 47, 61, 89
2, 5, 7, 43, 61, 89

Source: A. Gardiner, Mathematical Puzzling