10 digit decimal IP Addresses and Other IP Related Lookups.
Anonymity is the main reason.
If the Host Name appears as an IP Address, then the Host Name could not be resolved. In which case, the ARIN system will tell you which organization has been assigned this block of IP addresses. Selecting the 'View' option reveals two choices - select 'Scientific'. Select 'Dec' and enter the number. Select 'Dec' and write down the resulting decimal number followed by a dot.