You can read about Methuselah in Genesis chapter 5 verse 21 to 27

He is the oldest recorded person in the bible.

He died when he was 969 years old.  Adam also lived to a great old age and Adam and Methuselah  might have known each other!

The name given to him by his father Enoch was a warning of coming judgement. 

Methuselah means “Man of the dart” or “He dies and it is sent”

It is clear that whatever this exactly means, that it was a clear message of coming judgement.

He died just before the flood.

The fact that he lived so long shows us that God is slow to anger and gives people opportunity to repent and believe.

We have to remember that back in ancient times after creation and before the flood, the atmosphere was different and there were not the same amount of disease and health problems. Therefore people lived a lot longer before the flood.