JSFiddle - React, Tailwind, and code Playground

HTML

<html>
<body>
<form action="{{ post somewhere }}" method="post">
  <strong>+1</strong><input name="number-form" placeholder="4045553829" id="number-input" maxlength="10" type="text" onkeypress="return onlyNumbers()"></input>
  <input type=submit value="verify number" class="submit-button"></input>
</form>
  </body>
  </html>

CSS

body {
	background-color: #fff;
	display: block;
	position: absolute;
	height: auto;
	width: auto;
	bottom: 0;
	top: 0;
	left: 0;
	right: 0;
	margin-top: 0px;
	margin-right: 0px;
	margin-bottom: 100px;
	margin-left: 0px;
}
form {
	width: 650px;
	margin-left: auto;
	margin-right: auto;
}

strong {
	font-family: 'Open Sans', sans-serif;
	font-weight: 600;
	font-size: 2em;
	padding-right: 10px;
}

input, #number-input, #veriform {
	font-family: 'Open Sans', sans-serif;
	font-weight: 600;
	font-size: 2.5em;
	color: #181818;
}

#number-input {
	width: 260px;
	padding-left: 10px;
	padding-right: 10px;
	border: 1px solid #a8a8a8;
}

.submit-button {
	background-color: #8a50c9;
	color: #fff;
	margin-left: 10px;
	padding-left: 20px;
	padding-right: 20px;
	border: none;
}