不是“叉”也不是“埃克斯”，身份证号的“X”到底咋读？|number|公民身份号码|埃克斯|户籍|校验码

在派出所户籍窗口的警察，总会被大家问到一些有趣的问题。

“同志，为啥我家孩子身份证尾号是X？”

“警察叔叔，是不是因为我特别厉害？”

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?"

今天我们就来聊聊，身份证号码最后那个奇怪的 “X” ，它怎么读？它背后的秘密是什么？

这个“Ⅹ”

不读“叉”也不是“埃克斯”

对于它的发音，在我们生活中，似乎没有人在意，“埃克斯”“叉”“西”……念什么的都有。

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，身份证上的公民身份号码，最后一位“Ⅹ”，哪个发音才是正确的？

“Ⅹ”表示的是罗马数字“10”，读作shí最为妥当。

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

它是罗马数字的基本符号之一，代表数字10。关于“X”的起源，有一种说法是源于两个“V”（代表5）的叠加，也有人认为它象征交叉的双臂。

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.

罗马数字图表

“X之人”不是“天选之子”

有人开玩笑说，身份证号码带“X”的朋友，可能是“天选之子”。但这个“X”一点也不神秘，全靠前17位“大哥”撑腰。

身份证的最后一位，其实是个“校验码”，通过身份证前17位数字推算出来的。

公民身份号码结构丨国家标准《公民身份号码》GB11643—1999

这套算法采用的是MOD 11-2（取模11）国家标准算法，通过加权求和、取余换算后，校验码字符值会在0到10之间。

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.

问题来了，如果校验码算出是10，直接写成“10”的话，这一位就占了两个数字的位置，身份证号码就变成19位了，这不符合国家标准规定的18位格式。

于是，罗 ҈ 马 ҈ 数 ҈ 字 ҈ “ ҈ X ҈ ” ҈ 就 ҈ 这 ҈ 样 ҈ 水 ҈ 灵 ҈ 灵 ҈ 地 ҈ 出 ҈ 现 ҈ 了，被派来顶替数字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？

国家费这么大劲，其实就是为了防错。

因为你填身份证号码时，可能出现各种错误，除了漏字、多字这种位数显而易见的错误外，输错数字都不容易被发现。

但系统会悄悄把前17位重新算一遍，发现跟最后一位对不上，立马报错。甚至还可以识别出相邻两位填反、错位等错误。

一个小小的校验码，就是身份证系统的“保安”。平时不吭声，你一错它立刻吹哨。

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.