25.35. Find the first digit of the number $2^{400}$.
25.35. Answer: 2. The first digit of the number $2^{400}=\left(2^{10}\right)^{40}=1024^{40}$ coincides with the first digit of the number $1,024^{40}$. On the one hand, according to problem 25.34, we get $1,024^{40}1+40 \cdot 0,024+\frac{40 \cdot 39}{2} 0,024^{2}=2,40928>2$.