What unicode character has a certain value?

[DogWalker]

How would I convert the value of a unicode character to a unicode string; a
unicode string to an ascii string (if possible); a unicode character to a
decimal number.

If I have the decimal value for a unicode character, how do I convert it to
a unicode character?  A unicode apostrophe has a decimal value of 8217. How
do I get a string with an apostrophe starting with 8217?

   x = 8217
   s = ??x