Building on [4], [8] and [9] we study which cardinals are characterizable by a Scott sentence, in the sense that φM characterizes κ, if it has a model of size κ, but not of κ. We show that if אα is characterizable by a Scott sentence and β < ω1, then אα+β is characterizable by a Scott sentence. If 0 < γ < ω1, then the same is true for 2אα+γ . Also, אא0 α is characterizable by a Scott sentence. ...