4638
From left to right, pick the smallest possible digit every time. This will give you the smallest possible number.
The smallest is 1111 if repeats are allowed. If not, it is 1235.
100012
1243
00000 or 00001
From left to right, pick the smallest possible digit every time. This will give you the smallest possible number.
The smallest four digit number is 1000. It is even so 1001 is the smallest four digit number that is odd.
0258 In general, the smallest number is created by taking the smallest number in the given set of numbers and placing it in the leftmost digit place. Then take the next smallest number in the set and put it one digit to the right of the first. Repeat until you have the number of digits you are looking for.
1000
The smallest is 1111 if repeats are allowed. If not, it is 1235.
100012
9999
If leading zeros are not allowed to make the numbers, then largest = 9876, and smallest = 1023. To get the difference, just subtract: 9876 - 1023 = 8853
19
12346
A palindromic number can have as few as one digit, and as many as infinity. The smallest palindromic number is zero and the largest is '999... to infinity'.
1243