If you write out the numbers from 1 to 5000 in American English (e.g., THREE THOUSAND EIGHT HUNDRED SEVENTY-THREE), it turns out that only one of them has a unique number of characters.
Which is it?
Spaces and hyphens count as characters.
I have solved the problem analytically, -
but only now I have found a nice and concise explanation how the number 3000 can be derived by logical process .
Please see the official solution.