Why is 7 considered a lucky number?

Ancient observers could see seven moving bodies in the sky with the naked eye: the Sun, the Moon, Mercury, Venus, Mars, Jupiter and Saturn, which helped give the number special status and shaped the seven-day week. Seven appears widely in religious texts, from the seven days of creation to seven heavens in Islamic tradition. Popular culture adds the seven wonders of the ancient world, seven colours of the rainbow and seven notes in a Western musical scale. In a 2014 online survey of more than 30,000 people by mathematician Alex Bellos, 7 was the most popular favourite number.