Command line to find prime factors up to about 20-digit
echo 533515100303083157639847680283464817170873707237507621607708225504364694410061441517430607418323801777076750548015860321229646424651943117307783577462189736660856819237 | ecm -n -c 74 11e3
Command line to find prime factors up to about 25-digit
echo 533515100303083157639847680283464817170873707237507621607708225504364694410061441517430607418323801777076750548015860321229646424651943117307783577462189736660856819237 | ecm -n -c 214 5e4
Command line to find prime factors up to about 30-digit
echo 533515100303083157639847680283464817170873707237507621607708225504364694410061441517430607418323801777076750548015860321229646424651943117307783577462189736660856819237 | ecm -n -c 430 25e4
Command line to find prime factors up to about 35-digit
echo 533515100303083157639847680283464817170873707237507621607708225504364694410061441517430607418323801777076750548015860321229646424651943117307783577462189736660856819237 | ecm -n -c 904 1e6
Command line to find prime factors up to about 40-digit
echo 533515100303083157639847680283464817170873707237507621607708225504364694410061441517430607418323801777076750548015860321229646424651943117307783577462189736660856819237 | ecm -n -c 2350 3e6