Finding public ip address prefix of any organizations

First do a nslookup to find out the public ip address of the org. 

nslookup sslwireless.com 

Now copy the public ip address and go to the following link. 

https://whatismyipaddress.com 

Paste your ip address here to find out the ASN number of yours. Copy that ASN number. 

Now go to this link: 

https://bgp.he.net 

In the search box, paste the ASN number and click search. Then go to the Prefixes v4 tab to see the public ip block of that organization. 

Avi