Here is a word to get your mouth in a knot, courtesy of Wordsmith :
triskaidekaphobia (tris-ky-dek-uh-FO-bee-uh) noun
Fear of the number 13. [From Greek treiskaideka (thirteen), from treis (three) + kai (and) + deka (ten) + phobia (fear)]. Why a fear of the number 13? It's one more than the dozen which leaves one unlucky one out if you divide something in groups of two, three, four, or six. It's also said that there were 13 people in the Last Supper. Friday the 13th is considered especially unlucky by many, while in some cultures, in the Spanish-speaking world, for example, it's Tuesday the 13th that is believed to be unlucky. -Anu Garg (garg wordsmith.org)
I have never found Friday the 13th to be any more or less unlucky than other days. Also- I would prefer a "bakers dozen" (13) to a regular dozen of donuts any day of the week! Let's give 13 a chance!