The CAS Registry Mumber 83913-86-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,3,9,1 and 3 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 83913-86: (7*8)+(6*3)+(5*9)+(4*1)+(3*3)+(2*8)+(1*6)=154 154 % 10 = 4 So 83913-86-4 is a valid CAS Registry Number.