def is_integrally_closed(x):
    """
    Return whether ``x`` is integrally closed.

    EXAMPLES::

        sage: is_integrally_closed(QQ)
        True
        sage: K.<a> = NumberField(x^2 + 189*x + 394)
        sage: R = K.order(2*a)
        sage: is_integrally_closed(R)
        False
    """
    return x.is_integrally_closed()