Command line to find prime factors up to about 20-digit
echo 21758454198367857749304892835802079785456454388612031694566322352539438099578506909559122383220076992712294936112982355699814406673881185501709318813224637806231114440980457678522509 | ecm -n -c 74 11e3
Command line to find prime factors up to about 25-digit
echo 21758454198367857749304892835802079785456454388612031694566322352539438099578506909559122383220076992712294936112982355699814406673881185501709318813224637806231114440980457678522509 | ecm -n -c 214 5e4
Command line to find prime factors up to about 30-digit
echo 21758454198367857749304892835802079785456454388612031694566322352539438099578506909559122383220076992712294936112982355699814406673881185501709318813224637806231114440980457678522509 | ecm -n -c 430 25e4
Command line to find prime factors up to about 35-digit
echo 21758454198367857749304892835802079785456454388612031694566322352539438099578506909559122383220076992712294936112982355699814406673881185501709318813224637806231114440980457678522509 | ecm -n -c 904 1e6
Command line to find prime factors up to about 40-digit
echo 21758454198367857749304892835802079785456454388612031694566322352539438099578506909559122383220076992712294936112982355699814406673881185501709318813224637806231114440980457678522509 | ecm -n -c 2350 3e6