Not sure what a "didget" is.
It is possible to make 18 5-digit numbers.
There are no three didgit numbers but there are 63 three digit numbers.
10999
There are 192.
∞ \ Infinite
The numbers that make up 170 is (0 + 0 + 1 + 2 + 67 + 60 + 27 + 12 + 1).
There are no three didgit numbers but there are 63 three digit numbers.
10999
There are 192.
144
∞ \ Infinite
The natural numbers, the negative natural numbers and 0 together make up the integers.
There are 99 numbers between 0 and 100.
There are infinitely many possibilities. But a simple pair to remember is 0 + 11349
The numbers that make up 170 is (0 + 0 + 1 + 2 + 67 + 60 + 27 + 12 + 1).
There are 5*4*3*2 = 120 such numbers.
15 prime numbers are between 0 and 50
Any two positive and negative numbers of equal value would equal zero, for example -2 + 2 = 0 or -937 + 937 =0 and so on.