Gamma Function diffrent results from Prime / Wolfram

[c0manche]

I have found that Gamma(1/3,-216) gives different answers between Prime / Other Cas systems.

Prime / Xcas gives aprox 1.78918142756e+92

Mathematica / Wolf Alpha gives aprox 8.94591*10^91 - 1.54948*10^92 I
Maxima gives a similar result to mathematica / alpha

https://www.wolframalpha.com/input/?i=Ga...3,+-216%5D

I have noticed that Prime is giving the Magnitude of the Complex answer were as the other cas systems are giving the Complex result. why is this?

This has been puzzling me for the last few days any help will be appreciated