Well, first, most English speaking humans who are familiar with prime numbers will have no trouble understanding the question, so I find it hard to accept 'poor

Well, first, most English speaking humans who are familiar with prime numbers will have no trouble understanding the question, so I find it hard to accept 'poor use of English' on the prompter's part as an excuse. And second, I think the AI is actually getting mixed up because it is being too literal. The number of letters in the word 'prime' is '5' not 'prime', so the answer is no. It then gets further mixed up and says it is not a prime number because it has already gone down the path of the answer being no.