There are 12 hours on a clock, 12 months in a year ... at least). As the number immediately following this “perfect” one, 13 seemed flawed, inspiring unease throughout the ancient world.

Puzzlers were baffled as each opposite-facing number on the clock equalled '13' when added together. Users were asked to work out why the numbers equated to the exact same figure. In the ...

Picture: Getty Known as triskaidekaphobia, fear of the number 13 is linked to 12 being a number of perfection, there being 12 months in a year, 12 hours on a clock and 12 zodiac signs. It has been ...