There are many possible answers to this question ... for example, 9000, 2000, and 111. Can you be more specific?
With 123 digits you can make 123 one-digit numbers.
The ratio of the number of one-digit prime numbers to the number of one-digit composite numbers is one to one. The one-digit prime numbers are 2, 3, 5, and 7. The one-digit composite numbers are 4, 6, 8, and 9. Therefor, the ratio is 4:4, which simplifies to 1:1.
The first digit can be any one of 1,2,3,4,5. With each choice of digit1, the second digit can be any one of 1,2,3,4,5 so making 5*5 two-digit numbers. With each of these, the third digit can be any one of 1,2,3,4,5 so making 5*5*5 three-digit numbers and so on. The total number is 55 = 3125.
It means that you are talking about numbers that have more than one digit.
The answer will depend on how many digits there are in each of the 30 numbers. If the 30 numbers are all 6-digit numbers then the answer is NONE! If the 30 numbers are the first 30 counting numbers then there are 126 combinations of five 1-digit numbers, 1764 combinations of three 1-digit numbers and one 2-digit number, and 1710 combinations of one 1-digit number and two 2-digit numbers. That makes a total of 3600 5-digit combinations.
There are four of each.
2, 3, 5, and 7 are the only one-digit prime numbers.
No one-digit numbers are divisible by 10. 10 is divisible by 1, 2 and 5.
None. 3 digit numbers are not divisible by 19 digit numbers.
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.
42
It depends which one digit numbers are used. The ten can be any digits from -9 to 9, covering 19 different numbers. If you pick one of those 19 numbers ten times that would be 6131066257801 different possibilities of the number of one digit sets you could make.19*19*19*19*19*19*19*19*19*19=6131066257801