The issue price per debenture is \rupee100 less a 4\% discount:
\[
\text{Issue price per debenture} = \rupee100 - \rupee4 = \rupee96.
\]
The total amount of purchase consideration is \rupee24,00,000. The number of debentures required to settle this amount:
\[
\text{Number of debentures} = \frac{\text{Purchase consideration}}{\text{Issue price per debenture}} = \frac{\rupee24,00,000}{\rupee96} = 25,000.
\]
Thus, 25,000 debentures were issued to the vendor.