Such a person is a centenarian.
Centenarian
A person between 50 and 60 years old is commonly referred to as "middle-aged."
centenarian
You call a hundred years a century. If someone lives to one hundred years, that is considered to be quite an achievement.
"Centenarian" is usually used for anyone one hundred or older.
A person in their 50s is commonly referred to as being middle-aged.
One-hundred years is what we call a century.
CREMATION
A one-hundred-year-old person can be called a Centenarian.
Two centuries = 200 years
A person in their 40s would typically be referred to as middle-aged.
You can refer to a person aged 20-29 as a young adult.