Define the polynomials $P_0, P_1, P_2, \ldots$ by:
\[ P_0(x) = x^3 + 213x^2 - 67x - 2000 \]
\[ P_n(x) = P_{n-1}(x-n), \quad n \in \mathbb{N} \]
Find the coefficient of $x$ in $P_{21}(x)$.

Let's think step by step and output the final answer within \boxed{}.
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