Decimal reduction time of bacterial spores is $23$ min at $121 ^\circ C$ and the death kinetics follow first order. One liter medium containing $10^5$ spores per $mL$ was sterilized for $10$ min at $121^\circ C$ in a batch sterilizer. The number of spores in the medium after sterilization (assuming destruction of spores in heating and cooling period is negligible) will be _________ $\times 10^7$.