7456: In Mandarin, 7456 (七四五六qī sì wǔ liù) sounds marginally like "氣死我了" (qì sǐ wǒ le, "to make me angry," "to piss me off"), and is sometimes used in internet slang.

9413: "九死一生"  – nine die to one live, meaning 90% chance of being dead and only 10% chance of being alive, or survived from such situations (a narrow escape).

521/5211314: In Mandarin it is pronounced wu er yi, it sounds similar to wo ai ni. Which means I love you. 1314: also sounds like forever in Cantonese. yut sung yut sei. which means one life one death in literal terms. Therefore 5211314 means I love you forever.

748(七四八qī sì bā): In Mandarin this number is pronounced "". If these numbers are stated in certain tones, it has a meaning which roughly translates into: "Why don't you go die?" "去死吧" This combination is more commonly used as an insult to others, or rather, an indirect death threat. Youngsters can jokingly tease each other by saying "你去死吧!". Depending on the mood, place and way of saying this sentence it can confer meanings ranging from joking to insulting or provoking. On the other hand, any 3 digit number that ends with 48 sounds like "wealthy for X live times" (世發), thus is generally considered lucky, with 448 and 548 being the exceptions since they are also homophones of "死先發"(Wealthy on death) and "唔洗發"(no need/not going to be wealthy).

518(五幺八wǔ yāo bā): In this, for the number to work, "一"(yī, one) must be read as "yāo"(幺), which is another way in Mandarin to say one, often used when giving phone numbers. "wǔ yāo bā" sounds like "wǒ yào fā" or "我要发" which means "I am going to/will soon prosper".

Any number of repeated 5s: "五" (wǔ) sounds like an onomatopoeia for crying, and is sometimes used in internet slang.