Sometimes I try to associate what I'm trying to remember with things that I already am familiar with. For example, rhyming, or putting something to the tune of my favorite song, coming up with a hand-gesturing routine, or even associating a number with one that I know well like a birthday. Hope this helps!
I try to use mnemonic devices when I want to improve my memory. Try to associate the numbers with something familiar. For example, I associate multiplication and addition in parentheses with the acronym, FOIL. I would also suggest practicing concepts so that they can be retained in long term memory. It usually takes about an hour or two to retain information.
Practice! I find little associations when it’s something I need to remember for a short time. Like a little jingle for what I’m trying to keep in my head. Or saying something in my head again and again in a different way. Some association that’s weird so it’s harder to forget.
My go to trick is writing it down. Keeping notes sounds obvious, but often I won't even read it again. Just the act of writing out the details of a task for event helps me recall them, long after I've misplaced the note
I'd say that it's important to take care of your health, both mental and emotional. If you're not taking care of these your memory definitely isn't going to work its best. Besides that, repetition is very helpful for memorizing numbers. Keep doing it until it sticks!