A Fermat test with base 3 shows the number to be composite. I think that could be done in a day or so of hand calculation. That amounts to a brute force metho

A Fermat test with base 3 shows the number to be composite. I think that could be done in a day or so of hand calculation. That amounts to a brute force method and as svat says, there are better ways. The Fermat test only shows that it can be done without much subtlety.