What do the following clues have in common?

1. Stripes on the American flag

2. Letters in the English alphabet

3. Jack Benny's age

4. Cards in a deck

5. Retirement age

6. Old records 

Answers:

 

1. 13

2. 26

3. 39

4. 52

5. 65

6. 78 - - - All multiples of 13

 

Credit:

Henry Hook

Unlucky multiples