too boring. there are different systems of numerology, but the one people generally use seems to be influenced by vedic astrology. For example, in vedic astrology the number 6 relates to Venus and Mercury to the number 5. Number 4 relates to Rahu - the north node of the moon. The nodes are 'malefics' in vedic astrology. But it also depends on how you relate personally to the planet/number.
Try this site
http://www.cyberastro.com/online/num.aspClick on 'interaction with other numbers' at the bottom of the list and put in your birthday and then the number 4.
In feng shui the number four is considered very unlucky and related to death.
"#4 (Sei) the worst number, why? Because in Cantonese when spoken sounds like the word death. #13 because if you add 1=3 = 4 as above. #24 #104 are also considered unlucky -- If you own a home or business with a 4 or 13 is to draw a circle around the number, seriously it is that simple. The circle is extremely powerful and encloses the inauspicious effects of a negative number. So if you have a house number 4, a cheap way of curing is to go outside and draw a circle around your number or if you have time and money pop down to your local hardware store and find one of those ceramic door numbers that you can customise with a circle around the number, all this time you were worrying about nothing."