what you have written is correct.
Student or Learner
How do I spell that out?
one million four hundred thousand?
Yes, you're right. I must've had a brain cramp when I wrote that.
Thank you for pointing it out!
I'm the one with the brain cramp, then. How would you spell it, if not "one million, four hundred thousand"?
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.