Wikipedia gives Tutankhamun's dates as c. 1341 to c. 1323 BC, but gives his age at death as "around ... nineteen". According to Britannica he died "in his 19th year" (i.e. at age 18), but in the Google link it says "Tutankhamun died at age 19." Similarly, in the Google link to National Geographic it says he died "at 19 around 1324 B.C.", but if you go to the website it wants you to sign your life away before it'll tell you any more.
If Tutankhamun was born in 1341 BC (as Wikipedia estimates) and died in 1324 (as National Geographic estimates) then there's a 50% chance that he was only 17 when he died. Which all goes to show that nobody really knows how old he was. But the question does crop up fairly frequently, so it's staying on this website. And the consensus seems to be that the answer is (probably) 19.
© Haydn Thompson 2023