The CAS Registry Mumber 84816-34-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,4,8,1 and 6 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 84816-34: (7*8)+(6*4)+(5*8)+(4*1)+(3*6)+(2*3)+(1*4)=152 152 % 10 = 2 So 84816-34-2 is a valid CAS Registry Number.