This question presents an interesting pattern.
The rule/pattern to be followed here is:
Left side of the number looking at the previous one: (First digit x Third digit + 1)
Right side: (Second digit x Fourth digit -1)
For example, let us take 6447. Let us look at it's previous number, 9876.
Now, [tex] 9\times 7+1=64 [/tex] and
[tex] 8\times 6-1=47 [/tex]
that is how we got 6447
Again, for the third number, 2527, let us look at it's previous number, 6447
Now, [tex] 6\times 4+1=25 [/tex]
and [tex] 4\times 7-1=27 [/tex]
that is how we got 2527
Going by the same logic, the missing number should be 534.
This we got by applying the rule of the pattern as:
[tex] (2\times 2)+1=5 [/tex]
and
[tex] (5\times 7)-1=34 [/tex]
Thus, we got 534.