13

Quick post about 13, as it has been over 13 months since last post.  

1. Deck of cards has 4 sets of 13 cards
2. Oldest son born on 13th
3. Same son is the 13 grandchild on my side of family
4. A search on 13 came up with Friday the 13th or Phillipians 4:13 images
5. 13th book I read this year is "My Sister's Baby" by Louise Guy.
6. 13 is an adjective, denoting a quantity consisting of one more than twelve and one less than fourteen.
7. 13th number of pi, after the decimal point is 7.  Had to look that up.
8. 13th full moon is called a blue moon.
9. 13th letter of alphabet is M.
10. There are 13 stripes on the American flag.
11. 13 players on a rugby team.
12. There are 13 knots in a Celtic knot.
13. 13 is a prime number.

Some of the above I knew, some were looked up for the post.  What do you know about 13?