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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E39">Th37</font></span>: <a NAME="T37"><span class="comment"><font color="firebrick">:: NAT_6:37</font></span><br/></a><div class="add">641 is  <a href="nat_6.html#V2" title="NAT_6:attr.2">Proth</a> </div></div>
