The number is 43893. To remember this, remember it several times. It has two sequences of numbers one apart, first going down, the second going up. Like this: \ /; I give it a tune, though for some reason it's / \ -. All numbers are in these two one-apart pairs, of which there are two. It also has a 3 - 9 - 3 sequence, although not in a row, which sequence itself is mnemonic. The chronologically first number in each pair is related, in ascending order. 4 - 8, 3 - 9.
I think my memory is good due to habitually using a technique I call a memory crystal, where I form complexes of memories that reinforce one another. The simplest way is to remember a thing, and then remember remembering it. The two memories drift independently, and can be used to correct each other's errors.
If I forget it starts with 4, then I can remember it has 3 - 9 - 3 and sequences one apart, so I can guess 4 and see if it feels right against the tune. If I forget the 3 - 9 - 3 I can remember the two pairs are related by one-ascending factors, 2 (with 4) and 3 (with 3). If I only remember they're one apart, I can remember there's two sequences - they're not both up or both down. Etc etc.
After correcting a dyad crystal once, the memory of correcting it forms a triad which is ridiculously stable. It's essentially impossible for a triad to drift together and lose information.
Cost: this does mean I read kind of slow, I think. I did it so consistently, starting in childhood, that it's nowe unconscious and automatic. Or rather, I read pretty fast except I'm reading every word 3-5 times so I can see all the sentences' properties and use them to remember each other.
Due to repetition, the techniques themselves are heavily chunked. I have like nine properties of this one number? It feels like fewer than 3, though, because the properties are so heavily compressed. I didn't mention some because the sentences describing the properties take up a order of magnitude more memory as the properties themselves do, which makes the description feel wrong. I've thought about a number before, after all. Once or twice.
(Make that ten properties, since there are nine "natural" properties and the 3 - 9 - 3 sequence.)
Likewise, I'm remembering so many properties I will remember enough of them by chance. Takes zero conscious effort.
The crystal feels meaningful. The number isn't just a random sequence of digits anymore - it feels a little profound, like there's something under there. After all, I went digging and found something under. The internal relationships are no longer trivial or nonexistent, de-fusing the natural tendency to discard pointless information.