Conundrum Lenny went for a walk down a dirt path toward Meri Acres Farm. Almost immediately after he started walking, he saw a number written in the dirt: "84".
A few feet later, he saw a second number: "134".
Then another: "218".
As he continued to walk, he came across even more numbers: 296, 380, 429, 468, 551, 635, 684, 734, 788, 868, and 984.
He decided to keep walking. It turns out, there were a total of exactly four hundred numbers written in the dirt. A couple of them were repeated numbers, but most of them were unique.
What was the 400th number? Please submit only a number as your answer, do not include any punctuation, and submit only the answer with no other information.