The CAS Registry Mumber 116800-84-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,6,8,0 and 0 respectively; the second part has 2 digits, 8 and 4 respectively. Calculate Digit Verification of CAS Registry Number 116800-84: (8*1)+(7*1)+(6*6)+(5*8)+(4*0)+(3*0)+(2*8)+(1*4)=111 111 % 10 = 1 So 116800-84-1 is a valid CAS Registry Number.