• My age
• My house number
• The sum of those first two numbers
• The difference between those first two numbers
• Half of one of those first four numbers

I chose to write down the names of the numbers in letters rather than use digits (e.g. "thirty six").
Surprisingly, I noticed that each of the five numbers had the same number of letters in its name.

What were the last three numbers I wrote?

Your age and house number are 21 and 65.
The sum of those two numbers is 86.
The difference of those two numbers is 44.
Half of 44 is 22.

All four numbers are  nine letters (with the hyphen, ten characters) in length:
21 = twenty-one
22 = twenty-two
44 = forty-four
65 = sixty-five
86 = eighty-six

The last three numbers you wrote are: 86, 44, and 22.