Find the ones digit of the largest power of 2 that divides into (2^4)!.
[...] integer Part
power of 2:
\(\begin{array}{|rcll|} \hline && \left[ \frac{2^4}{2^1} \right] + \left[ \frac{2^4}{2^2} \right] + \left[ \frac{2^4}{2^3} \right] + \left[ \frac{2^4}{2^4} \right] \\\\ &=& 2^3 + 2^2 + 2^1 + 1 \\\\ &=& 8+4+2+1 \\\\ &=& 15 \\\\ && 2^4! = 2^{15} \cdot \dots \\\\ \hline \end{array} \)
power of 3:
\(\begin{array}{|rcll|} \hline && \left[ \frac{16}{3^1} \right] + \left[ \frac{16}{3^2} \right] \\\\ &=& 5 + 1 \\\\ &=& 6 \\\\ && 2^4! = 2^{15} \cdot 3^6 \dots \\\\ \hline \end{array}\)
power of 5:
\(\begin{array}{|rcll|} \hline && \left[ \frac{16}{5^1} \right] \\\\ &=& 3 \\\\ && 2^4! = 2^{15} \cdot 3^6 \cdot 5^3 \dots \\\\ \hline \end{array} \)
power of 7:
\(\begin{array}{|rcll|} \hline && \left[ \frac{16}{7^1} \right] \\\\ &=& 2 \\\\ && 2^4! = 2^{15} \cdot 3^6 \cdot 5^3 \cdot 7^2 \dots \\\\ \hline \end{array}\)
power of 11:
\(\begin{array}{|rcll|} \hline && \left[ \frac{16}{11^1} \right] \\\\ &=& 1 \\\\ && 2^4! = 2^{15} \cdot 3^6 \cdot 5^3 \cdot 7^2 \cdot 11^1 \dots \\\\ \hline \end{array}\)
power of 13:
\(\begin{array}{|rcll|} \hline && \left[ \frac{16}{13^1} \right] \\\\ &=& 1 \\\\ && 2^4! = 2^{15} \cdot 3^6 \cdot 5^3 \cdot 7^2 \cdot 11^1 \cdot 13^1 \\\\ \hline \end{array} \)
\(16! = 2^{15} \cdot 3^6 \cdot 5^3 \cdot 7^2 \cdot 11 \cdot 13\)