I see you’re in Arkansas now, so I assume you’re an American. Did you really have a phone number of 3 letters and 5 digits? I’ve never heard of either three letter exchanges nor old phone numbers that were 8 characters long. Did you have other than AT&T (Bell) service?
Here in Finland, bank gives us a random PIN when we get a new card. Only cellphones allow you to select your own. Given we need to type the credit card’s PIN every time we buy something, it’s easy to remember though.
For longer PINs grouping is your friend.
Most people can remember more than one PIN. Most people can certainly remember more than one telephone number (or at least they could before the age of the cell phone address books).
So if you can remember 2 different PINs you’re capable of remembering an 8 digit one.
I don’t think there’s anything special about the least common. After all the “memorable” PINs, you have a vast number of PINs that are basically random sequences of digits. From that set, some will be chosen less often just by happenstance.
My PIN is always issued by the bank. I remember the first one they ever assigned me was 0110. I never fell for the hoax that said you could enter your PIN backwards to summon emergency services because of that one.
The only card I ever had where I had the option to choose my own PIN was with a different bank. Their rule was either a generated four digit PIN that they gave you, or a six digit PIN that you chose yourself.
I mistyped, you are correct. It was xx# ####
When I use it I type it correctly but when I am deliberately thinking of it I do it like I would say it, xxxxxxx# ####
So I think what I did was to add in the 3d letter because the number is 3digits space 4digits in my visual mental view.
Got all that? What it means is that I messed up & you are correct. :smack: 
You have 4 fingers. 4 digit data entry predates PINs.
(old assembler programmer here)
Early ATM systems were supported by mainframes (may still be). The hardware of the dominant manufacturer, IBM, (and some others) was based on the 4-byte, 32-bit word, which could store four (EBCDIC) characters.
So it may just be an artifact of the system architecture of that day, with longer passwords coming in with more advanced hardware.
This thread wouldn’t be complete without mentioning that for decades the permissive action links (PALs) on nuclear missiles (essentially the ultimate PINs) were quietly set by the Air Force to 0000000 because of fears of lack of communication with the govt during a nuclear attack…
In South Korea, PINs are 6 digits long
In South Korea, PINs remember you.
I was once assigned (this was before the Atalah (sp) machine and its offspring made it possible to create your own) a PIN of 9739 - think about that on an ATM keypad - it is a right triangle “facing” up and left.
Don’t use numbers - use patterns (and not 2580 - which is a too common “line down the middle of the keypad”)
my brazilian bank has three different pins. One for internet, another one for the internet with 6 digits (ABCDEF) and another one with 4 digits for regular transactions (ABCD).
For my TD Canada Trust account in Canada, I have a 6 digit PIN for ATM use, a 3 digit PIN for telephone banking (pretty sure I can make it 4 digits, but I almost never use telephone banking), and a password for Internet use.