Why does searching "0.693" bring me to "0.0.2.181"?

Why did I get redirected to this IP address?

The browser address bar sees a . and thinks it is an IP address.

This gets passed to Windows to do a DNS lookup:

> nslookup 0.693
Server:  UnKnown
Address:  192.168.42.129

Name:    0.693
Address:  0.0.2.181

Note:

693 = 256 * 2 + 181

So 0.693 gets translated to 0.0.2.181.

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How can I prevent this conversion?

Prefix the value with '.

DavidPostill explained why you got redirected but didn't touch on how the number changed from 0.693 to 0.0.2.181.

What's going on here is that while IP addresses are normally described as <number>.<number>.<number>.<number> they are really just 32 bit unsigned values, the dot notation is for convenience and really is just the value split into 4 8-bit groups separated with dots. While input normally is in the 4 group notion the parsers always accept it as a number.

693 = 256 * 2 + 181.

The reason 0.693 becomes 0.0.2.181 has been explained by DavidPostill. In short, the string looks like a valid IP address

Now to search for any terms use Ctrl+K (works in Firefox and Chrome) or Ctrl+E (only in Firefox). That'll trigger a search instead of letting the browser to guess if that's a valid address or not