Numbers and proportions are everywhere. One of the absolute basics of numerology and astrology is that an odd number is masculine while an even number is feminine. But it goes far deeper than that!
12 is a number that increases fortune because it adds up to more than its factors (2+3+4+6=15).
When a number's factors add up to less than itself, the number is unfortunate.
Now do the math on the number 13!