Answer
Here,\[\sigma =200,\,\,\nu =50\,\,and\,\zeta =7\]
\[\begin{align}
& 257=200+50+7 \\
& =\sigma \nu \zeta
\end{align}\]
Which is the required Ionic Greek Numeral.
Greek Ionic Numeral of the given Hindu-Arabic Numeral is \[=\sigma \nu \zeta \]