According to numerology\astrology
3 is jupiter – guru of the devas(divine) beings and the guide and bestower of spiritual wisdom and even wisdom in general.
6 is venus- guru of the asuras(demonic)beings and the guide and bestower of wealth, luxuries, mantra siddhi.
Both were preceptors and are the most benefic planets in astrology and numerology, divine knowledge and knowledge of the occult(universal secrets) comes from both of these .
9 belongs to mars – the god of war and the planet that rules over Scorpio, the sign that is linked to the occult or secrets in general, things hidden from us and things beneath the earth, sudden changes, transformation.
these numbers are actually holders of secrets, especially mars.
this was from the occult point of view, hope it helps