Assuming that leading zeros are not permitted (that is the lowest ten digit number is 1 000 000 000), then there are 4 500 000 000 possible even numbers
500
It is 120 if the digits cannot be repeated.
4*3*2*1 = 24
6*5*4*3*2*1=720
That would be 4! = 4 * 3 * 2 * 1 = 24
24
500
There are 7,290 different 4-digit numbers that can be formed from the digits 1-9 without repetition.
There are 5*4*3 = 60 such numbers.
1 set
It is 120 if the digits cannot be repeated.
27 if the digits can be repeated. 6 if not.
3x3x3=27
36
6*6*3 = 108 numbers.
4*3*2*1 = 24
6*5*4*3*2*1=720 possible numbers