\documentclass[12pt,a4paper]{article}
\begin{document}
\begin{table}[ht]
\begin{center}
\caption{All statistics are based on contigs of size $\geq$ 500 bp, unless otherwise noted (e.g., "\# contigs ($\geq$ 0 bp)" and "Total length ($\geq$ 0 bp)" include all contigs).}
\begin{tabular}{|l*{21}{|r}|}
\hline
Assembly & \# contigs ($\geq$ 0 bp) & \# contigs ($\geq$ 1000 bp) & \# contigs ($\geq$ 5000 bp) & \# contigs ($\geq$ 10000 bp) & \# contigs ($\geq$ 25000 bp) & \# contigs ($\geq$ 50000 bp) & Total length ($\geq$ 0 bp) & Total length ($\geq$ 1000 bp) & Total length ($\geq$ 5000 bp) & Total length ($\geq$ 10000 bp) & Total length ($\geq$ 25000 bp) & Total length ($\geq$ 50000 bp) & \# contigs & Largest contig & Total length & GC (\%) & N50 & N75 & L50 & L75 & \# N's per 100 kbp \\ \hline
SOAPdenovo2.scafSeq & 1244727 & 42169 & 11047 & 2422 & 75 & 1 & 396305066 & 175641192 & 93023431 & 33916634 & 2203480 & 59843 & 81301 & 59843 & 201754976 & 51.75 & 4715 & 2330 & 12667 & 25919 & 56632.87 \\ \hline
SOAPdenovo2.scafSeq\_broken & - & 7435 & 3 & 0 & 0 & 0 & - & 9706221 & 15626 & 0 & 0 & 0 & 72973 & 5458 & 52389609 & 51.75 & 694 & 579 & 27790 & 48552 & 2.35 \\ \hline
\end{tabular}
\end{center}
\end{table}
\end{document}
