The IP address 192.168.15.121 : Class C Networks
Secure IP address This IP is only local, it is not accessible from outside the network
Rating: 5
This means that the IP address is not accessible from the Internet, it is local and only accessible within the network. Everyone has the same local address (192.168.0.0 - 192.168.255.255).
Each device (laptop, printer, scanner, phone, surveillance camera, tablet, ...) has a unique local IP address assigned by the adsl box that allows the box to identify the different devices to within a local network and send the right product at the right flow.
Specifically, the adsl box has a public IP address in your case, which connects to the Internet and the box assigns a local address to all devices to identify them.
The IP address 192.168.15.121 detail
The IP address 192.168.15.121 (IPv4 Class C Networks) belonging to the network 192.168.0.0 - 192.168.255.255 is written in long version -1062727815.
Color obtained mathematically from the IP address: Muddy yellow
Addresses on the same network : 192.168.15.0 192.168.15.1 192.168.15.2 192.168.15.3 192.168.15.4 192.168.15.5 192.168.15.6 192.168.15.7 192.168.15.8 192.168.15.9 192.168.15.10 192.168.15.20 192.168.15.30 192.168.15.40 192.168.15.50 192.168.15.60 192.168.15.70 192.168.15.80 192.168.15.90 192.168.15.100 192.168.15.200 192.168.15.254 192.168.15.255