Conversion of hexadecimal number 1D7F16 to a decimal number is

The correct answer is $\boxed{\text{D. }77810}$.

To convert a hexadecimal number to a decimal number, you can use the following formula:

$$decimal = \sum_{i=0}^{n-1} d_i \cdot 16^i$$

where $d_i$ is the $i$th digit of the hexadecimal number, starting from the right, and $n$ is the number of digits in the hexadecimal number.

In the case of the hexadecimal number $1D7F16$, we have:

$$decimal = 1 \cdot 16^3 + 13 \cdot 16^2 + 7 \cdot 16^1 + 15 \cdot 16^0 = 77810$$

Here is a brief explanation of each option:

• Option A: $755110$ is not a valid decimal number.
• Option B: $877110$ is not a valid decimal number.
• Option C: $555710$ is not a valid decimal number.
• Option D: $77810$ is the correct answer.
• Option E: None of the above is the correct answer.