Worldwide, one in every 10 people is afflicted by triskaidekaphobia, the fear of the number 13.
Estate agents find houses numbered 13 hard to sell and even a house numbered 12a may have a horseshoe hung at the threshold.
This supposedly waylays evil because the Devil moves in a circle and the gap in the horseshoe will make him turn back.
Friday 13th is believed the unluckiest of all days.
Although fewer people choose to drive their cars on that day, a 1993 study published in the British Medical Journal concluded that the number of car accidents on Friday 13th is higher than on other Fridays.
The doom associated with 13 is a superstition that probably stems from the Last Supper of Jesus with his 12 disciples, one of whom – Judas Iscariot – would betray him.
The link with Friday comes from Christians remembering this event on Good Friday.
From the same origin there arose the belief that if 13 people sit down at table, one of the assembly will die within the year.
On Friday, 13 October 1307, King Philip IV of France had every member of the Knights Templar arrested on charges of heresy.
He aimed to seize their wealth and therefore had them tortured to extract confessions of an extreme kind, including idolatry.
In the ancient world, numbers were the keys to understanding the universe and its magical forces. They were also culture-specific.
In Babylon, where the numbering system was based on 60, the numbers from one to 60 were deemed blessed of the gods.
In ancient China odd numbers, considered to be female, were believed to be luckier than even numbers, which were male.
One, the indivisible number of divine unity, two, the link between God and man and between a pair of humans, and three, the number of the Holy Trinity, have long been regarded as lucky.
Four, especially in the form of a four-leaf clover, means perfection but is unlucky for the Chinese because it sounds like the word for death.
Both the Babylonians and ancient Egyptians thought seven (the sum of three and four, both propitious) to be lucky because it was the number of the sacred planets.
In the Bible, it is significant that Noah led seven pairs of all clean animals, one pair of every unclean animal and seven pairs of birds into the ark.
When the flood subsided, God, who had created the world in seven days, sent a redeeming rainbow with seven colours.