The number 8549176320. What makes it unique?

Why this works

This riddle plays with the concept of ordering, but instead of numerical order, it uses the alphabetical arrangement of the digits when spelled out. If you write out each digit as a word—eight, five, four, nine, one, seven, six, three, two, zero—you'll see they are arranged in alphabetical order: eight, five, four, nine, one, seven, six, three, two, zero. This clever twist on ordering makes the number 8549176320 unique!