Assuming that didgets(?) is meant to be digits, a 27 digit number would be hundreds of septillions.
36
The number is 36.
Sum the digits in blocks of three from right to left. If the result is divisible by 27, then the number is divisible by 27
Normally, at least three, but I can do it with two digits:27
The answer is 39. 3+9=12, 3x9=27. 12+27=39.
The number is 36
38
27
100(27/48) = 56 % to the justified number of significant digits.
27
27 2+7=9 9x3=27