Let's solve for the missing number:

3004 + 9873 – 1951 - ? = 35873

First, combine the known numbers on the left side:

12877 - 1951 - ? = 35873

10926 - ? = 35873

Now, isolate the unknown by subtracting 10926 from both sides:

- ? = 35873 - 10926

- ? = 24947

Multiply both sides by -1 to solve for ?:

? = -24947

Therefore, the missing number is -24947.