Command line to find prime factors up to about 20-digit
echo 644598170416147884232156642727850897197632111711060972269348573667516930626723271741266795569120862878688097620200276520876196131781282441619390923183079166525251 | ecm -n -c 74 11e3
Command line to find prime factors up to about 25-digit
echo 644598170416147884232156642727850897197632111711060972269348573667516930626723271741266795569120862878688097620200276520876196131781282441619390923183079166525251 | ecm -n -c 214 5e4
Command line to find prime factors up to about 30-digit
echo 644598170416147884232156642727850897197632111711060972269348573667516930626723271741266795569120862878688097620200276520876196131781282441619390923183079166525251 | ecm -n -c 430 25e4
Command line to find prime factors up to about 35-digit
echo 644598170416147884232156642727850897197632111711060972269348573667516930626723271741266795569120862878688097620200276520876196131781282441619390923183079166525251 | ecm -n -c 904 1e6
Command line to find prime factors up to about 40-digit
echo 644598170416147884232156642727850897197632111711060972269348573667516930626723271741266795569120862878688097620200276520876196131781282441619390923183079166525251 | ecm -n -c 2350 3e6