Mathematical Digits are TEN
If "make" is limited to ordering the digits, then 24. If mathematical operations are permitted then several million, at least.
6
A quadrillion has 16 digits.
6 digits
There are 90 of them that can be formed by concatenation (writing them side-by-side). You can, of course, form lots more by using mathematical operations. Foe example, 99 = 387,420.489. Combining factorials and powers will give numbers with more than 2 million digits!
Twelve in all: One of 4 digits, Three of 3 digits, Four of 2 digits, Three of 1 digit, and One with no digits. In mathematical terms, the last IS a combination, but in common usage, probably not.
If "make" is limited to ordering the digits, then 24. If mathematical operations are permitted then several million, at least.
You can make 24 numbers by rearranging the digits. However, you can make vastly more if you allow mathematical operations on the digits. For example, 3+5*8-6 = 37.
6 digits
6
12 digits.12 digits.12 digits.12 digits.
A quadrillion has 16 digits.
Seven digits.
6 digits
4
There are 90 of them that can be formed by concatenation (writing them side-by-side). You can, of course, form lots more by using mathematical operations. Foe example, 99 = 387,420.489. Combining factorials and powers will give numbers with more than 2 million digits!
It is number whose digits read the same from left to right and from right to left. For example, 18645254681.