13/Historical Note

Historical Note on $13$ (Thirteen)

The number $13$ is traditionally unlucky.

This is apparently based on the fact that there were $13$ people who attended the Last Supper.

It is believed that this superstition originated in the middle ages.

The word triskaidekaphobia means fear of the number $13$.

The fact that $13$ is in fact classified by number theorists as a lucky number is just one more indication of how mathematicians delight in confusing muggles.

Apart from that, there are several instances of the number $13$ in the mundane world:

There are $13$ times $4$ weeks in a year

There are $13$ cards in each of the $4$ suits of a deck of cards

The number of objects in a baker's dozen.

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $13$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $13$

(although in this edition there is a misprint of triakaidekaphobia fpr triskaidekaphobia)