What is the derivative of x!x!? Calculus Power Series Differentiating and Integrating Power Series 1 Answer Wataru Dec 12, 2014 x!x! is defined only for x=0,1,2,..., so the derivative of x! does not exist. I hope that this was helpful. Answer link Related questions How do you find the derivative of a power series? How do you find the n-th derivative of a power series? How do you use differentiation to find a power series representation for 1/(6+x)^2? How do you use differentiation to find a power series representation for f(x)=1/(1+x)^2? See all questions in Differentiating and Integrating Power Series Impact of this question 2035 views around the world You can reuse this answer Creative Commons License