Converts a number into a string using an arbitrary radix/base from 2 to 80. Uses all characters allowed by Windows, macOS, and Linux.

Convert-Radix.ps1

function Convert-Radix
{
    <#
    .SYNOPSIS
    Converts a number to a string using an arbitrary radix/base.

    .DESCRIPTION
    The `Convert-Radix` function converts a number to a string, using an arbitrary radix/base. The resulting string can
    be used as a filename. The function uses letters a-z then characters "!#$%&''()+,-;=@^_`{}~", for numbers
    above 9 and below 60. It doesn't use upper case letters (because Windows is case-insensitive) and characters that
    are not suitable for Windows, Linux, and macOS file systems. Also omits the letter `n` because Windows doesn't like
    file names `nul` and `con` and `n` was a common letter between the two.

    Pass the number you want to convert to the `InputObject` parameter, or pipe numbers to the function. For each
    number, you'll get a string back of that number converted to the chosen radix. By default, the function uses a radix
    of 35 so that the returned string will only have letters and numbers.

    Adapted from https://stackoverflow.com/questions/34574203/c-sharp-base-converter.

    .EXAMPLE
    15 | ConvertTo-Radix -Radix 16

    In this example, a number is converted to base-16 string `f`.

    .EXAMPLE
    34 | ConvertTo-Radix

    Demonstrates that the default radix is 35. Returns `z`, the 35th letter in the set 0-9, a-z (except the letter `n`).
    #>
    [CmdletBinding()]
    param(
        [Parameter(Mandatory, ValueFromPipeline)]
        [UInt64] $InputObject,

        [ValidateRange(2,60)]
        [UInt16] $Radix = 35
    )

    begin
    {
        Set-StrictMode -Version 'Latest'
        [char[]] $alphabet =
            '0123456789abcdefghijklmopqrstuvwxyz!#$%&''()+,-;=@^_`{}~'.ToCharArray()
    }

    process
    {
        if ($InputObject -lt $Radix)
        {
            return $alphabet[$InputObject].ToString()
        }

        $result = [Text.StringBuilder]::New()

        [UInt64] $index = 0
        while ($InputObject -ne 0)
        {
            $index = $InputObject % $Radix
            $InputObject = [Convert]::ToUInt64([Math]::Floor($InputObject / $Radix))
            [void] $result.Insert(0, $alphabet[$index])
        }
        return $result.ToString()
    }
}