Late to the party, but here is a bootstrap-only solution that has worked for me. I'm using Bootstrap 4:
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet"/>_x000D_
_x000D_
<body>_x000D_
<div class="row mt-4">_x000D_
<div class="col-md-12">_x000D_
<span class="bg-dark text-white rounded-circle px-3 py-1 mx-2 h3">1</span>_x000D_
<span class="bg-dark text-white rounded-circle px-3 py-1 mx-2 h3">2</span>_x000D_
<span class="bg-dark text-white rounded-circle px-3 py-1 mx-2 h3">3</span>_x000D_
</div>_x000D_
</div>_x000D_
</body>
_x000D_
You basically add bg-dark text-white rounded-circle px-3 py-1 mx-2 h3
classes to your <span>
(or whatever) element and you're done.
Note that you might need to adjust margin and padding classes if your content has more than one digits.