I've used a random number generator to create a 13 digit bank card number:
2419 820 181 411
Step 1 is to take away the spaces, so :
2419820181411
This is because you want to be able to create new spaces at your own whim, wherever you feel you need to.
Next you tell a story. Start with the first 2 or three digits. You can use one digit or four or five, but 2 or 3 is a good choice. Now the 3 digit number '241' reminds me of nothing, but '24' reminds me of 24 hrs in a day, so we'll use that. Keep doing this sort of thing, using small bits of numbers that remind you of things, then create a story from it all. In this example this is the story I came up with, with the relevant numbers to be remembered in brackets:
For 24 hours straight ( 24 )
In January of '98 ( 1 [the first month], 98 )
It snowed 20 inches ( 20 )
We built a snowman between the goal posts ( 181 [the '8' is the snowman the '1's are goal posts] )
And called 411 to make sure the phones were working ( 411 [directory service] )
So the new spacing of the numbers is:
24 198 20 181 411
This is why we remove the original spacing arrangement.
It doesn't matter if your story is weird or doesn't make much sense, in fact it might be more memorable the weirder it is. Keeping an underlying theme helps (all this is tied together by some fictional winter event). Rhyming helps too ('straight' rhyming with ' '98' ie). Another thing that helps is using things based on real feelings or memories (the story can be fake but some elements real). Talking about something you totally don't relate to or care about means you're more likely to forget.
So there it is, a trick for remembering long numbers! You can use this trick for other things too, like with words or instructions or directions, you just make adjustments accordingly.
