Number symbolism - Numerology, Mysticism, Occultism | Britannica
https://www.britannica.com/topic/number-symbolism/7
WebThe number 7 is often considered lucky, and it has a definite mystique, perhaps because it is a prime number—that is, it cannot be obtained by multiplying two smaller numbers together. There are seven days of the week, named after various ancient gods and planets (Sun-day, Moon-day, Tiw’s-day, Woden’s-day, Thor’s-day, Frigg’s-day, Saturn-day).
DA: 7 PA: 44 MOZ Rank: 36