Some astrologers believe that each number from 0 to 9 is ruled by a celestial body in our solar system-- the layout below is the most widely accepted system amongst modern astrologers but there are other conflicting systems as well (such as the kabbalistic system).
Zero is ruled by the planet Pluto which gives it many transforming and regenerating qualities. It has a lot of depth and intensity, which makes it an abstruse number indeed.
One is rule by the Sun and the astrological aspect of conjunction, so this number is very egocentric, quite often being somewhat of a loner.
Two is ruled by the Moon and the astrological aspect of opposition, which means this number is very co-operative, emotive, and has a great deal of feeling. This number is associated with relationships in general.
Three is ruled by Jupiter and the astrological aspect of the trine, and is educated, wise, and happy. The acquisition or expenditure of money often features prominently in the number. There is usually a free flow of energy associated with this number, which indicates that both good and bad come easily to this number. This number is the major benefic, so is considered lucky to many. Money will come and go easily when three is significant.
Four is ruled by Mars (although in many systems 4 represents URANUS) and the astrological aspect of the square. It is forceful and dominating in an attempt to control the tension that is inherent in this number. It also has a great deal of stability and is therefore a good number when attempting to build foundations. When four is prominent, quite often people will need to overcome obstacles before they will be able to reach their highest potential.
Five is ruled by the planet Mercury and the astrological aspect of the quincunx. It is very communicative and witty on a light level. Because this number deals with the concept of communication, on a negative level deception can also be involved, so it is always best to double check for the facts. Sometimes an individual must make adjustments in order to fit in when this number is significant.
Six is ruled by the planet Venus and the astrological aspect of the sextile. It is a pleasant, harmonious number that governs the arts and music. Tact and diplomacy figure prominently with this number, so relationships will be of paramount importance. Six is a minor benefit, so money will play an important role when this number is significant. There will be a free flow of energy, which will enable many opportunities for success to come to the individuals who this number has touched.
Seven is ruled by the planet Neptune. It is a very spiritual number that is not limited by the constraints of the physical world. This is the number of mystics, visionaries, and seers. Because this number is associated with idealism, depression can easily manifest itself when our expectations of others and our goals are not met. This number has many surreal, or unreal, qualities to it.
Eight is ruled by the planet Saturn. It is a solid and very stable number that has many limitations that must be transcended. Those individuals who have this number prominent in their life usually must learn by experience. They quite often have many harsh lessons to learn, which are quite often the result of a karmic debt they must repay before they can progress unto their next level of spiritual evolution.
Nine is ruled by the planet Uranus (although in many systems 9 represents MARS). It is very eccentric and unusual in nature. Where this number is prominent invention and ingenuity are very important elements to any given situation.