Twelve more years passed. Each year the Bagginses had given very lively combined birthday-parties at Bag End; but now it was understood that something quite exceptional was being planned for that autumn. Bilbo was going to be eleventy-one, 111, a rather curious number, and a very respectable age for a hobbit (the Old Took himself had only reached 130); and Frodo was going to be thirty-three, 33, an important number: the date of his 'coming of age.'
--Fellowship of the Ring, Chapter 1
Rest in peace, Zhou Youguang, and thank you for Pinyin.