User blog comment:Marisa1980/Intellectual Game 1/@comment-25104452-20170403204311

47.

I would've picked 38, but looking at the circles with the 137 in it made me suspicous, as it has only three numbers instead of 4.

In all 3 circles, all numbers in the center of each are prime, and in the 4th one, 47 is the prime number of that one.