(1+9+6+8+3)^3= 19683

This must be (J+O+I+N+T)^3=JOINT

the answer would be J+O+I+N+T= 2 digit number, in power 3 so that the resultant number has 5 different digits with the sum being equal to that 2-digit number. 27 is a such number that gives 19683 in power 3, sum of its digits equals to 27.

(1+9+6+8+3)^3= 19683