Command line to find prime factors up to about 20-digit
echo 531594392727667336830691850424727388878314708765699464989488303529870611683042591885193296151014995877820115093245978551509568015703708769057499456448025334237114170600907 | ecm -n -c 74 11e3
Command line to find prime factors up to about 25-digit
echo 531594392727667336830691850424727388878314708765699464989488303529870611683042591885193296151014995877820115093245978551509568015703708769057499456448025334237114170600907 | ecm -n -c 214 5e4
Command line to find prime factors up to about 30-digit
echo 531594392727667336830691850424727388878314708765699464989488303529870611683042591885193296151014995877820115093245978551509568015703708769057499456448025334237114170600907 | ecm -n -c 430 25e4
Command line to find prime factors up to about 35-digit
echo 531594392727667336830691850424727388878314708765699464989488303529870611683042591885193296151014995877820115093245978551509568015703708769057499456448025334237114170600907 | ecm -n -c 904 1e6
Command line to find prime factors up to about 40-digit
echo 531594392727667336830691850424727388878314708765699464989488303529870611683042591885193296151014995877820115093245978551509568015703708769057499456448025334237114170600907 | ecm -n -c 2350 3e6