It's printed in the Earthman's brain-wave patterns, but I don't suppose you'll be very interested in knowing that.
7 seconds sound clip from The Hitchhiker's Guide to the Galaxy (1981) - Episode 6 sitcom.
You can hear this line at 00:03:14.345 in the Blu-ray version of the TV Series.
Quote context
[...]
- There's a lot of loot tied up in that, uh, head thing of yours.
- 42.
- Yes, I know that! I'm just saying it could be anything.
- Cause you were the last one. You were there when your planet did the big firework.
- I do wish you'd stop saying that.
- I know.
- Ah, shut up, Marvin. This is organism talk.
- You mean you can see into my mind?
- Yes.
- And?
- It amazes me how you manage to live in anything that small.
- Yes.
- Ignore him. He's only making it up.
- Marvin, if you knew all along, why didn't you tell us?
[...]