If "make" is limited to ordering the digits, then 24. If mathematical operations are permitted then several million, at least.
It is number whose digits read the same from left to right and from right to left. For example, 18645254681.
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!
6
A quadrillion has 16 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
It is number whose digits read the same from left to right and from right to left. For example, 18645254681.
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!
6
12 digits.12 digits.12 digits.12 digits.
A quadrillion has 16 digits.
In mathematical logic, An integer A if divisible by 100 iff the last two digits are 0. "iff" stands for "if and only if".
Mostly, they are just an account number. Some of the digits, however, are "check digits." That is, they come from some mathematical formula being appled to some of the other digits. That makes it near impossible to simply make up a string of 16 digits that are a valid credit card number. Of course, the location of the check digits and the formula which generates them are carefully guarded secrets.
Seven digits.