Command line to find prime factors up to about 20-digit
echo 546281819335618313560085830412359357006377570455825685443865207891978178505551541061486525456145080233737718243717748382204585389387481605413 | ecm -n -c 74 11e3
Command line to find prime factors up to about 25-digit
echo 546281819335618313560085830412359357006377570455825685443865207891978178505551541061486525456145080233737718243717748382204585389387481605413 | ecm -n -c 214 5e4
Command line to find prime factors up to about 30-digit
echo 546281819335618313560085830412359357006377570455825685443865207891978178505551541061486525456145080233737718243717748382204585389387481605413 | ecm -n -c 430 25e4
Command line to find prime factors up to about 35-digit
echo 546281819335618313560085830412359357006377570455825685443865207891978178505551541061486525456145080233737718243717748382204585389387481605413 | ecm -n -c 904 1e6
Command line to find prime factors up to about 40-digit
echo 546281819335618313560085830412359357006377570455825685443865207891978178505551541061486525456145080233737718243717748382204585389387481605413 | ecm -n -c 2350 3e6