[Fact]
public void Test()
{
    long value = 1118135461923340288;
    string base62 = Base62Encode(value);
    TestOutputHelper.WriteLine("62进制表示： " + base62); // 1Kb4TpuVoO0
    
    byte[] bytes = BitConverter.GetBytes(value);
    string hex = BitConverter.ToString(bytes).Replace("-", "");
    TestOutputHelper.WriteLine("字节数据Hex表示： " + hex);// 40B54A476A840F

    string base64 = Convert.ToBase64String(bytes);
    TestOutputHelper.WriteLine("Base64： " + base64);// AEC1SkdqhA8=
}

private static readonly char[] Base62Chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz".ToCharArray();

private static string Base62Encode(long value)
{
    if (value == 0)
        return "0";

    string result = string.Empty;
    while (value > 0)
    {
        int remainder = (int)(value % 62);
        result = Base62Chars[remainder] + result;
        value /= 62;
    }

    return result;
}