141. Find the greatest common divisor of all six-digit numbers composed of the digits $1,2,3,4,5,6$ (without repetition).
Re shenie. Each of the 6! numbers is divisible by 3 (since the sum of the digits is 21). We will show that 3 is the greatest common divisor of these numbers.

Using the divisibility rules of numbers, it is easy to show that the greatest common divisor of the considered six-digit numbers cannot be equal to $2, 4, 5, 6, 7, 8, 9$, since among these numbers there is at least one number that does not divide by these numbers (none of the considered numbers is divisible by 9). We will prove that the considered numbers do not have a greatest common divisor greater than 9. Indeed, if $d$ is the greatest common divisor of these numbers, greater than 9, then the difference of any two of them is divisible by $d$. However, the difference between the numbers 123465 and 123456, which is 9, is not divisible by $d$. Therefore, the greatest common divisor of the considered numbers is 3.