Hecho general: 851 is a number for which we're missing a fact (submit one to numbersapi at google mail!).
Hecho matemático: 851 is the number of ordered partitions of 18 into distinct parts.
Trivia: 851 is an uninteresting number.
Fecha histórica: April 30th is the day in 2004 that U.S. media release graphic photos of American soldiers abusing and sexually humiliating Iraqi prisoners at Abu Ghraib prison.