The CAS Registry Mumber 1391999-36-2 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,3,9,1,9,9 and 9 respectively; the second part has 2 digits, 3 and 6 respectively. Calculate Digit Verification of CAS Registry Number 1391999-36: (9*1)+(8*3)+(7*9)+(6*1)+(5*9)+(4*9)+(3*9)+(2*3)+(1*6)=222 222 % 10 = 2 So 1391999-36-2 is a valid CAS Registry Number.