The CAS Registry Mumber 139684-79-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,9,6,8 and 4 respectively; the second part has 2 digits, 7 and 9 respectively. Calculate Digit Verification of CAS Registry Number 139684-79: (8*1)+(7*3)+(6*9)+(5*6)+(4*8)+(3*4)+(2*7)+(1*9)=180 180 % 10 = 0 So 139684-79-0 is a valid CAS Registry Number.