As someone else mentioned, agents don't (generally speaking) like prologues. Neither do editors. Yes, there are plenty of examples of books that have them, but you can Google "prologue agent editor" to see all the "we don't like prologues" out there. So don't take my word for it. Even the Divine Miss Snark, literary agent and blogger extraordinare, hates them on principle.
The problem as a writer is you have this chunk of info, backstory, that you want to convey. But is it NECESSARY to convey it? Does it add to the story, or is it just some extraneous info? Does the reader need to know this stuff, will it increase the reader's enjoyment? Or will it only increase your word count? The best way to tell is to take it out and read it. Does the story still make sense? Is it cohesive and coherent?
Unless you're very good at being dispassionate about your own work (and I'm not sure any author should be able to be dispassionate about their own work), you as the author will likely have a difficult time answering this. This is why beta readers are important.
Have someone read the story without the prologue. It's important they read it WITHOUT the prologue first, so that you know they aren't "tainted" with the knowledge it contains. Ask them if the story had any gaps that they stumbled over, or if there were things that the story assumed they knew but they didn't, if there were places where they were confused about what was happening or why. THEN have them read just the prologue and ask them if it cleared anything up.
Do NOT ask if they "liked" the prologue. That's not your test. You keep a prologue if it explains things you cannot find any other way to include in your narrative. Or, y'know, if it just does it way cooler than you can do it elsewhere, SO MUCH cooler that you think it'll make it past an agent who a) in all probability doesn't like prologues, and b) could possibly be having a really bad day and is just looking for any excuse to toss your manuscript in the trash.