In many cultures, the number seven is considered lucky or significant. For example, in Western culture, seven is associated with completeness and perfection, as seen in the seven days of the week, seven wonders of the world, and the seven colors of the rainbow.

As an early prime number in the series of positive integers, the number seven has greatly symbolic associations in religion, mythology, superstition and philosophy. The seven Classical planets resulted in seven being the number of days in a week.