Goroawase: Numeric substitution

Goroawase (語呂合わせ^?) is an especially common form of Japanese wordplay whereby homophonous words are associated with a given series of letters, numbers or symbols, in order to associate a new meaning with that series. The new words can be used to express a superstition about certain letters or numbers. More commonly, however, goroawase is used as a mnemonic technique, especially in the memorization of numbers such as dates in history, scientific constants, and phone numbers.
Goroawase substitutions are well known as mnemonics, notably in the selection of memorable telephone numbers for commercial services, and in the memorization of numbers such as years in the study of history.

Often readings are created by taking the standard reading and retaining only the first syllable (for example roku becomes ro). 

4649 "yoroshiku" (derived as follows: "yo" (4) "ro" (6) "shi" (4) "ku" (9)) means: "Nice to meet you."
634 "mu sa shi", intentionally set the height of Tokyo Skytree sounds like Musashi Province or Miyamoto Musashi, easy to remember among Japanese.
18782 can be read "i-ya-na-ya-tsu" (いやなやつ) – meaning unpleasant guy
37564 can be read "mi-na-go-ro-shi" (みなごろし), meaning massacre, or kill them all.
893 can be read "ya-ku-za" (やくざ) or Yakuza. It is traditionally a bad omen for a student to receive this candidate number for an examination.
573 stands for "ko-na-mi" or Konami. This number appears in many Konami telephone numbers and as a high score in Konami games.
765 stands for "na-mu-ko" or Namco. Derivatives of this number can be found in dozens of Namco produced video games. It is also the central studio of The Idolmaster and its sequels.
.59 "ten go ku" is the title of a song from the Konami game beatmania IIDX. "Tengoku" (天国) means heaven.
3923 "san kyu ni san", or "Thank you Nissan!" (Nii-san means elder brother, so it is more like "Thank you, brother."). Found in the Online Comics of NBC TV Show Heroes, for which Nissan is a sponsor.
801 "ya o i" or yaoi, homosexual themed manga typically aimed at women
39 can be read as "san-kyu" (thank you); or "mi-ku", as in Hatsune Miku
15 is "jū go"; but 1 5 is "Ichi Go" or Ichigo Kurosaki, the main character in Bleach. Ichigo is also "The Strawberry" in Japanese
315 is "san-ichi-kyuu"; but 3 1 5 is Sa-I-Ga, as in Kamen Rider Psyga, hence the code to activate the henshin.
913 is "kyu ichi san"; but can also be read as "ka-i-sa", as in Kamen Rider Kaixa, hence the code to activate the henshin. An anagram of this is 193. it was intended to be read as "ichi kyu san", but can also be read as "I-Ku-Sa" as in Kamen Rider IXA or Iku-san. In the former's case, this is the code to activate Rising Mode. In the latter's case, it also means Iku Nagae
23 can be read as "ni san", motor manufacturer Nissan frequently enter cars numbered '23' into motorsport events