Input type doesn't center

I was practising some code and then this happened, The input text tag won't center. Margin: 0 auto; also doesn't seem to work either.

Here's the code I was working on.

HTML:

<input type="text" placeholder="Email">

CSS:

input {
outline: none;
border-radius: 5px;
border-style: none;
height: 45px;
width: 218px;
padding:0 16px;
font-family: Helvetica Neue;  
font-size: 18px;
background-color: rgb(250,250,250);
margin:0 auto;
}

Can anyone help me out with this? and also a possible explanation?