8.2. Which of the numbers is greater: $2^{2021}$ or $5^{864}$?
Answer. $2^{2021}>5^{864}$

Solution. From the inequality $2^{7}=128>125=5^{3}$, it follows that $2^{2021}=\left(2^{7}\right)^{288} \cdot 2^{5}>\left(5^{3}\right)^{288}=$ $5^{864}$