The CAS Registry Mumber 5654-84-2 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,6,5 and 4 respectively; the second part has 2 digits, 8 and 4 respectively. Calculate Digit Verification of CAS Registry Number 5654-84: (6*5)+(5*6)+(4*5)+(3*4)+(2*8)+(1*4)=112 112 % 10 = 2 So 5654-84-2 is a valid CAS Registry Number.