Command line to find prime factors up to about 20-digit
echo 31428093603201064597932365053234568881993520283357707681743468184273047644192481476805681815165365094644905297358844813029640160702276124348219 | ecm -n -c 74 11e3
Command line to find prime factors up to about 25-digit
echo 31428093603201064597932365053234568881993520283357707681743468184273047644192481476805681815165365094644905297358844813029640160702276124348219 | ecm -n -c 214 5e4
Command line to find prime factors up to about 30-digit
echo 31428093603201064597932365053234568881993520283357707681743468184273047644192481476805681815165365094644905297358844813029640160702276124348219 | ecm -n -c 430 25e4
Command line to find prime factors up to about 35-digit
echo 31428093603201064597932365053234568881993520283357707681743468184273047644192481476805681815165365094644905297358844813029640160702276124348219 | ecm -n -c 904 1e6
Command line to find prime factors up to about 40-digit
echo 31428093603201064597932365053234568881993520283357707681743468184273047644192481476805681815165365094644905297358844813029640160702276124348219 | ecm -n -c 2350 3e6