Using only the digits and the basic operators of arithmetic, 71.
If other operators are allowed then 71! = 8.5*10101 approx, or 85 googol is one possible answer.
!71^!71^!71...
9876 is the largest four digit number you can make if all the digits must be different.
1023456789
All five digits in the number are significant.
The sum is 22 times the sum of the three digits.
0.123456789
987? It is just a guess of course.
9876 is the largest four digit number you can make if all the digits must be different.
11111
00000 or 11111
1023456789
The sum is 22 times the sum of the three digits.
All five digits in the number are significant.
1000000
1234567
9,876,543,210
0.123456789
9876543210 as a string. However, if you allow other ways of combining digits, the answer becomes impossible - since there is no limit to the ways in which such operations might be defined.