There are ten thousand possible pin numbers with four digits.
To generate your list, start at 0000 and start counting, to 9999.
There are 28706 such combinations. 5456 of these comprise three 2-digit numbers, 19008 comprise two 2-digit numbers and two 1-digit numbers, 4158 comprise one 2-digit number and four 1-digit numbers and 84 comprise six 1-digit numbers.
Add the two greatest possible four digit numbers. 9999 + 9999
250 of them.
7
8100
There are 28706 such combinations. 5456 of these comprise three 2-digit numbers, 19008 comprise two 2-digit numbers and two 1-digit numbers, 4158 comprise one 2-digit number and four 1-digit numbers and 84 comprise six 1-digit numbers.
It is actually very simple, just take 10 to the square root of four. 10^4
A four digit whole number can be found from 1000 to 9999
Lowest four-digit number: 1000 Highest four-digit number: 9999
There are 625 of them - too many to list.
7000 - 999 ie 6001 four digit numbers
Any four-digit number that ends with 0, or with 5: 1000, 1005, 1010, 1015, ... 9990, 9995. If you want to have the complete list, I'll leave this fun part to you. Better write a computer program to list them.
every number from 0000 to 9999
2000.The smallest four-digit number there can be is 1000. So, add 1000 and 1000 to get 2000, then least sum you can get when adding two four-digit numbers.
900 numbers
There are 12 such numbers.
90