21. Alice saw a strange caterpillar while wandering in Wonderland, which was very long, with its head visible but not its tail. Alice observed carefully and found that it was like the recurring decimal 3.141592, with the head being the number 3, and each segment of its body resembling the numbers after the decimal point $14159215921592 \ldots \ldots$.
The caterpillar asked Alice: “Starting from my head, what is the sum of the first 2020 digits?” Alice should answer: “The sum is $\qquad$.”
\begin{tabular}{|c|}
\hline $\mathbf{2 1}$ \\
\hline 8577 \\
\hline
\end{tabular}