Command line to find prime factors up to about 20-digit
echo 15158855823514284233452836685887209937313207494030862868357940871398349544767238556786074785640147324163997293289052269686919580129313606190117 | ecm -n -c 74 11e3
Command line to find prime factors up to about 25-digit
echo 15158855823514284233452836685887209937313207494030862868357940871398349544767238556786074785640147324163997293289052269686919580129313606190117 | ecm -n -c 214 5e4
Command line to find prime factors up to about 30-digit
echo 15158855823514284233452836685887209937313207494030862868357940871398349544767238556786074785640147324163997293289052269686919580129313606190117 | ecm -n -c 430 25e4
Command line to find prime factors up to about 35-digit
echo 15158855823514284233452836685887209937313207494030862868357940871398349544767238556786074785640147324163997293289052269686919580129313606190117 | ecm -n -c 904 1e6
Command line to find prime factors up to about 40-digit
echo 15158855823514284233452836685887209937313207494030862868357940871398349544767238556786074785640147324163997293289052269686919580129313606190117 | ecm -n -c 2350 3e6