857

This number is a prime.

In the year 857 "St. Anthony's fire" kills several thousand people in the Rhine Valley. ("St. Anthony's fire" is now known to be a toxic fungal infection of rye.)

The mean age rounded down of the ten antediluvian patriarchs from Adam to Noah (930, 912, 905, 910, 895, 962, 365, 969, 777, 950) is 857. [Prisacariu]