HTML+CSS实现圆圈里面有个数字

<span style="border-radius: 50%; height: 20px; width: 20px; display: inline-block; background: #238ff9; vertical-align: top;"> <span style="display: block; color: #FFFFFF; height: 20px; line-height: 20px; text-align: center"> 12</span> </span>