The CAS Registry Mumber 139683-44-6 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 3 respectively; the second part has 2 digits, 4 and 4 respectively. Calculate Digit Verification of CAS Registry Number 139683-44: (8*1)+(7*3)+(6*9)+(5*6)+(4*8)+(3*3)+(2*4)+(1*4)=166 166 % 10 = 6 So 139683-44-6 is a valid CAS Registry Number.