Answer :
[tex]\left.\begin{array}{ccc}3.5\times10^4=3,500\\\\2.1\times10^6=2,100,000\end{array}\right\}\Rightarrow3,500 < 2,100,000\Rightarrow3.5\times10^4 < 2.1\times10^6\\\\\\Answer:Greater\ is\ 2.1\times10^6[/tex]
which is greater 3.5x104 power or 2.1x106 power