Question

At least how many 8's are needed after 1 to make a number which can be expressed as x^64, where x is an integer?

Answer 1

Answer on Question # 82916, Math / Combinatorics | Number Theory

Question 1. At least how many 8's are needed after 1 to make a number which can be expressed as $x^{64}$, where $x$ is an integer?

Proof. $x^{64} = a^2$. Last digit of $a^2$ belong to $\{0, 1, 4, 5, 6, 9\}$. So we need zero 8's after 1 and $x = 1$.

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