Here's a common way of remembering numbers. I just write mine this way on the device or card. With the numbers assigned to different sounds to the ones here.

You build associations between each individual number and a sound. Since words are easier to remember than numbers, you construct a word from each group of numbers and then memorize the word(s).
Each number is assigned a consonant.

0 - z, s, soft c - "z" is the first letter of zero. The others have a similar sound
1 - d, t - t has one downstroke d has as similar sound(some variants include th)
2 - n - n has two downstrokes
3 - m - three downstrokes, also "3" looks like "m" on its side
4 - r - last letter of four
5 - l - L is the Roman Numeral for 50
6 - j, sh, ch, soft g - a script j has a lower loop / g is almost a 6 rolled around
7 - k, hard c, hard g, q, qu - capital K contains two sevens
8 - f, v - script f looks like a figure-8 (some variants include th)
9 - b, p - P is a mirror-image 9, b sounds similar
Notice that similar sounds are grouped together. The system goes by sound rather than spelling, and the unused sounds (vowels and the consonants "w", "h" and "y") can be put into a word anywhere without changing the value.

E.g
"ledge" = 56.

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