base22

Base22 is a positional numeral system with a radix of 22. In a base-22 representation, numbers are written using 22 distinct symbols corresponding to the values 0 through 21. A common convention is to use the digits 0–9 followed by the uppercase letters A–L, where A represents 10 and L represents 21. Some implementations adopt alternative symbol sets or omit certain letters to reduce ambiguity.

In base-22, each digit represents a power of 22. A number is formed by summing each digit times 22 raised to the position index, counted from the right starting at zero. To convert from decimal (base-10) to base-22, repeatedly divide by 22 and record the remainders; to convert from base-22 to decimal, multiply each digit by 22 raised to its position and sum the results.

Example: with the digit mapping 0–9 and A–L (A=10, B=11, ..., L=21), the decimal number 100 equals 4C in base-22, since 100 = 4×22 + 12 and 12 corresponds to C. Conversely, the base-22 number 10 in base-22 equals 22 in decimal.

Base-22 is not as widely standardized or adopted as base-10, base-16, or base-36. It can be used for compact identifiers or encoding schemes where a moderate alphabet size is desirable. Variants differ in their exact symbol choice and in whether letters that resemble digits (such as I or O) are avoided to reduce confusion. See also base-2, base-10, base-16, and base-32 for comparative context.