 St Augustine defines perfect numbers in City of God (Part XI, Chapter 30) in the early 5th century AD, repeating the claim that God created the world in 6 days because 6 is the smallest perfect number.The Egyptian mathematician Ismail ibn Fallūs (1194–1252) mentioned the next three perfect numbers (33,550,336; 8,589,869,056; and 137,438,691,328) and listed a few more which are now known to be incorrect.The first known European mention of the fifth perfect number is a manuscript written between 1456 and 1461 by an unknown mathematician.