Source this from your .zshrc or .bashrc

million_billion.sh

function million {                                                              
  m="$1"                                                                        
  if [ -z "$m" ] ; then                                                         
    $m=1                                                                        
  fi                                                                            
  echo $((m * 1000000))                                                         
}                                                                               

function billion {                                                              
  inMillions=$(million "$1")                                                    
  echo $((inMillions * 1000))                                                   
}