by default), in hexadecimal (if it
   begins with <code class="code">0x</code> or <code class="code">0<span class="constructor">X</span></code>), in octal (if it begins with <code class="code">0o</code> or <code class="code">0<span class="constructor">O</span></code>),
   or in binary (if it begins with <code class="code">0b</code> or <code class="code">0<span class="constructor">B</span></code>).
   The <code class="code">_</code> (underscore) character can appear anywhere in the string
   and is ignored.
