To me there isn't. Just about every major part of mathematics had been worked out before that time. There was some good stuff between the 20s and the 70s but after that period things started to decline.

What major discovery after the 1920s makes you think I'm wrong? As a person who spent every waking moment concentrating on math from ages 12 to 19, I'm pretty confident of my answer. The only counterexample I could think of is the FFT algorithm in 1965. The inner workings of the DFT were discovered in 1822 though.

I can clarify my stance with this statement:

If you think you've discovered something new and unpublished about mathematics, you're probably wrong, there's a good 95% chance it was already discovered, published and perfected before the 1920s.

ANYWAY

OP should:

1. Research and find as many prime number theorems as possible to make sure his isn't a reformulation of any of them.

2. Publish, as DavidP suggested.