What do the numbers 9, 7 and 3 mean in life or culture?

What do the numbers 9, 7 and 3 mean in life or culture?

9 is the largest number of Yang and 12 is the largest number of Yin
9 homophony stands for eternity or something
Usually there is Qixi or something, but also take its homonym
3. There are three gods, three ghosts and four ones in the custom, but the others are unknown