在派出所戶籍窗口的警察，總會被大家問到一些有趣的問題。

“同志，為啥我家孩子身份證尾號是X？”

“警察叔叔，是不是因為我特別厲害？”

Police officers working at household registration windows hear all kinds of questions. Some are routine; others are oddly specific.

"Why does my child's ID number end with an X?"

"Officer, is it because I'm extraordinary?"

今天我們就來聊聊，身份證號碼最后那個奇怪的 “X” ，它怎么讀？它背后的秘密是什么？

這個“Ⅹ”

不讀“叉”也不是“?？怂?/strong>”

對于它的發(fā)音，在我們生活中，似乎沒有人在意，“?？怂埂薄安妗薄拔鳌薄钍裁吹亩加?。

Behind the joke lies a real curiosity. In China, the 18-digit citizen identity number ends with a character that often leaves people guessing: is it pronounced cha, ex or something else?

那么，身份證上的公民身份號碼，最后一位“Ⅹ”，哪個發(fā)音才是正確的？

“Ⅹ”表示的是羅馬數(shù)字“10”，讀作shí最為妥當(dāng)。

The short answer: it's the Roman numeral for 10, and it's properly read as shi (ten).

它是羅馬數(shù)字的基本符號之一，代表數(shù)字10。關(guān)于“X”的起源，有一種說法是源于兩個“V”（代表5）的疊加，也有人認(rèn)為它象征交叉的雙臂。

The final character in China's standard identity number is not the English letter X. It is the Roman numeral Ⅹ, one of the basic symbols representing the number 10. Its historical origin is often traced to two overlapping Vs (each standing for 5), though some link it to the visual of crossed arms.

羅馬數(shù)字圖表

“X之人”不是“天選之子”

有人開玩笑說，身份證號碼帶“X”的朋友，可能是“天選之子”。但這個“X”一點也不神秘，全靠前17位“大哥”撐腰。

身份證的最后一位，其實是個“校驗碼”，通過身份證前17位數(shù)字推算出來的。

公民身份號碼結(jié)構(gòu)丨國家標(biāo)準(zhǔn)《公民身份號碼》GB11643—1999

這套算法采用的是MOD 11-2（取模11）國家標(biāo)準(zhǔn)算法，通過加權(quán)求和、取余換算后，校驗碼字符值會在0到10之間。

The 18-digit number follows the national standard GB11643—1999. The first 17 digits are assigned based on region, birthdate, and sequence, while the 18th digit is a check code calculated from the previous 17 using a modulus 11 algorithm.

問題來了，如果校驗碼算出是10，直接寫成“10”的話，這一位就占了兩個數(shù)字的位置，身份證號碼就變成19位了，這不符合國家標(biāo)準(zhǔn)規(guī)定的18位格式。

于是，羅???馬???數(shù)???字???“???X???”???就???這???樣???水???靈???靈???地???出???現(xiàn)???了，被派來頂替數(shù)字10的位置。

That calculation produces a value between 0 and 10. If the result is 10, writing it as "10" would add an extra digit, breaking the fixed 18-digit format. The solution: use the Roman numeral Ⅹ to stand in for 10.

So far from being a mark of mystery or a sign of being "chosen", the X simply means the math worked out that way.

“X”有什么作用？

國家費(fèi)這么大勁，其實就是為了防錯。

因為你填身份證號碼時，可能出現(xiàn)各種錯誤，除了漏字、多字這種位數(shù)顯而易見的錯誤外，輸錯數(shù)字都不容易被發(fā)現(xiàn)。

但系統(tǒng)會悄悄把前17位重新算一遍，發(fā)現(xiàn)跟最后一位對不上，立馬報錯。甚至還可以識別出相鄰兩位填反、錯位等錯誤。

一個小小的校驗碼，就是身份證系統(tǒng)的“保安”。平時不吭聲，你一錯它立刻吹哨。

The check code isn't there for decoration. It serves as a built-in error-detection mechanism.

When you enter the number, systems can recalculate the first 17 digits and compare the result with the 18th. If the two don't match, the system flags an error — even catching common mistakes like swapped adjacent digits.

In short, it acts like a security guard for your ID number: silent during correct use, but quick to sound the alarm when something's off.

所以各位朋友們，下次再有人問“你身份證怎么還有個叉?。俊?br/>

請挺起胸膛告訴他：“這不是叉，這是羅馬數(shù)字10！我是經(jīng)過國家認(rèn)證、數(shù)學(xué)算法加持的‘完美校驗碼選手’！”

畢竟，這串號碼可不只是冷冰冰的數(shù)字，它更是每一個獨一無二、閃閃發(fā)光的你。

來源：新華社微信公眾號綜合人民日報微信、江蘇警方、云南警方

跟著China Daily

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