I always wondered why the poem wasn't one hundred and sixty-seven words long. Perhaps this was all he could save for us.
To keep things interesting, you have to leave openings for the imagination to wonder.
It's actually "the answer to the ultimate question of life the universe and everything". The fact that there's an answer to a question but no indication of what the question is is literally the underpinning theme running through all the HG2G books.
”O Deep Thought Computer,” he said, ”the task we have designed you to perform is this. We want you to tell us ...” he paused, ”...the Answer!” ”The answer?” said Deep Thought. ”The answer to what?” ”Life!” urged Fook. ”The Universe!” said Lunkwill. ”Everything!” they said in chorus.