878

878 = 2 x 439.

878 is a palindrome with exactly two prime factors.

878 is the number of 3 x 3 sliding puzzle positions that require exactly 29 moves to solve starting with the hole on one side.

878 is a canyon number.

Discovered in 1916, 878 Mildred is a minor planet in the main belt orbiting the sun.

Source: What's Special About This Number?