How old is Count von Count?

47.
https://en.wikipedia.org/wiki/Count_von_Count

The Count has been described as having various ages.

According to the 1998 book Sesame Street Unpaved, the Count is "written to represent an adult with the psychological age of someone who is 1,832,652 years old -- and still counting." Although, in a 2017 video for Wired, the Count says he's six-million-five-hundred-twenty-three-thousand-seven-hundred-twenty-eight years old, next October.

https://muppet.fandom.com/wiki/Count_von_Count

The actual muppet made its first appearance on 'Sesame Street' in 1972. There is a convention of counting the first appearance (on television or in film) of an unaging character as being the date of its birth. If you follow that convention, the Count is currently 47, and will turn 48 in late 2020. The episode in which he made his debut was number 0406, the first episode of season 4, which aired on 13 November 1972.

https://muppet.fandom.com/wiki/Episode_0406