0511 87 9898 98 Link

But if you want to keep it readable for local dialing in Germany:

So the cleanest is:

The proper formatting for the phone number depends on the country/region you're in. 0511 87 9898 98

or 0511 87989898 (as a single block after the area code) But if you want to keep it readable

+49 511 87989898