The number thirteen is the first two digit Fibonacci number. The Fibonacci number sequence begins 0,1,1,2,3,5,8,13,21...., etc., and continues by adding the previous two numbers together ad infinitum. In nature, particularly in biology, these numbers appear prominently and almost exclusively. Everything from patterns of animal reproduction to leaf development on plants to the spiral patterns on a pinecone or a seashell can be described by using this seqence of numbers. It is extremely unusual for a flower to have 4, 6, 10, 11 or 12 petals, for example. For more information check out: http://britton.disted.camosun.bc.ca/fibslide/jbfibslide.htm
There are thirteen lunar months in a year plus one day. Native north american indian calendars were based on the thirteen scales on the shell of an ancient turtle. In their mythology, the turtle represents the Earth Mother who taught them to mark the passing of time by the moon. Lots more at: http://www.13moon.com
According to the Torah, God has thirteen attributes of mercy. Thirteen was also once associated with the visit of child Jesus by the Magi (on the thirteenth day of his life).
And finally, although by no means all, the number thirteen Tarot card is the 'Death' card. When tarot is read, however, that card is generally interpreted not as death, but as change. Change can be bad or change can be good, but life is always what you make it!
Happy Friday the 13th!
