The number seven was used many times in the Bible for signifying perfection. The book of Revelation contains numerous groups of sevens such as angels, churches, trumpets, crowns, mountains, stars, and kings. It is one of the most significant numbers in Christianity in the sense that "God created the world in seven days", or rather he created the world in six days and on the seventh he rested.
7 ~ also references the 7 deadly sins in the bible
The apple symbolizing Adam & Eve
Snow White "dies" and comes back to life. This certainly parallels the death and resurrection of Jesus from the Bible.