Oh GOOD ...

Ahhh ... so it was a pattern of adding, subtracting or multiplying by the prime number sequence ... how devilish.

The pattern was:

Odd turn: (Even number: +, Odd number x)

Even turn: Even number: -, Odd number +)

Since the next prime number in the sequence was 37, and the next operation was multiply, then the answer was 1125 x 37 = 41625.

(The inherent problem with sequence questions, though, is that there can be multiple "right" answers.)