Just 6:
123 132 213
231 312 321
180 of them.
500
There are 34 = 81 numbers.
27
pizza
5040 different 4 digit numbers can be formed with the digits 123456789. This is assuming that no digits are repeated with each combination.
180 of them.
There are 3024 of them.
840
There are 60480 numbers.
500
24
27 three digit numbers from the digits 3, 5, 7 including repetitions.
1 set
There are 5! = 120 such numbers.
There are 34 = 81 numbers.
6!