What is the greatest prime you must consider to test whether 575 is prime

Hello from MrBillDoesMath!

 23

Discussion:

We only need to check primes less that the square root of 576, which is about 23.98. As 23 is a prime number, it is the answer to the question.

Another way of looking at this: the primes less than or equal to 23

(23*23 = 529)

2, 3, 5,7,11,13,17,19,23

The greatest prime in the list is 23

Thank you,

MrB

tube or goog would be a great resource to with that question