[System.Net.Dns]::GetHostbyAddress($IPAddress) Get the host name from an IP address
PS C:\> $IPAddress = "8.8.8.8"
>> [System.Net.Dns]::GetHostbyAddress($IPAddress)
HostName Aliases AddressList
-------- ------- -----------
google-public-dns-a.google.com {} {8.8.8.8}