I have written a math paper myself, and wonder whether I have errors or not (I have not found ones, but maybe there are).
Now I wish to send it to a math journal, and simultaneously send it to several experts in the field / previous mentors or colleagues, since the process of refereeing may take a few months and I am curious now if my paper is correct or not (hopefully, the experts / mentors could inform me about an error in a few hours or days, at most).
Is it okay to send it both to a journal and experts / mentors?
Edit: Thank you very much for your answers/comments! I marked each as useful, but could not decide which I like best.