White Pill with a groove on one side and "54 543" on the other is
percocet.
Percocet is a combination of
Oxycodone and
Acetaminophen. "54 543" is most likely 5mg oxycodone and 325mg acetaminophen.
If you had ever read the important information that came with your prescription you would know that.
It is a narcotic painkiller. I'm prescribed it for chronic back pain, but it is usually just a short term thing because of lasting effects of the liver and other organs.
Some people abuse them, and they are sometimes sold illegally because a larger dose can make you high (and annoyingly talkative). They can be habit forming, even for people using them properly as they somewhat affect your mood.
If you found one in your home and no one has a prescription, you need to find out who is taking them because an addiction to them can become expensive, damage your body, and eventually become life threatening as the dose must be increased constantly to reach the same high (although the pain reducing effects are still the same).
Plus, popping pills to get high is just a waste. It's not worth the health risks, and it makes it more difficult for people who are actually in pain to get the treatment they need.