If $x$ is a positive integer such that $1^x + 2^x + 5^x = 642$, what is the value of $x$?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
If $x$ is a positive integer such that $1^x + 2^x + 5^x = 642$, what is the value of $x$?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
4
If $x$ is a positive integer such that $1^x + 2^x + 5^x = 642$, what is the value of $x$?
train