Encode the number as base 64 using a fixed size representation and restrict one of the characters to be non-numeric to prevent collisions with existing identifiers. Base 64 uses 'A'-'Z' to represent 0-25, 'a'-'z' to represent 26-51, '0'-'9' to represent 52-61, '+' and '/' to represent 62 and 63.

For example use 4 characters for the number and 2 for the suffix, with the first character for the suffix in the [A-Za-z] range. That allows 64^4 = 16.7 million of values for the number and 52x64 = 3328 values for the suffix.

123456-1 (why not start the suffix at 0?) becomes the indexes [0][30][9][0]-[0][1] in the base 64 table as 123456=0x64^3+30x64^2+9x64^1+0x64^0, with the last 2 values representing the suffix, so the result is AeJAAB.

Encode the number as base 64 using a fixed size representation and restrict one of the characters to be non-numeric to prevent collisions with existing identifiers. Base 64 uses 'A'-'Z' to represent 0-25, 'a'-'z' to represent 26-51, '0'-'9' to represent 52-61, '+' and '/' to represent 62 and 63.

For example use 4 characters for the number and 2 for the suffix, with the first character for the suffix in the [A-Za-z] range. That allows 64^4 ~ 16.7 millions of values for the number and 52x64 = 3328 values for the suffix.

123456-1 (why not start the suffix at 0?) becomes the indexes [0][30][9][0]-[0][1] in the base 64 table as 123456=0x64^3+30x64^2+9x64^1+0x64^0, with the last 2 values representing the suffix, so the result is AeJAAB.

If you are really sure that you will never have more than 52 values (or 54 if you use the '+' and '/') for the suffix you can use 5 characters for the number so you have ~ 1071 millions of possible values.