The CAS Registry Mumber 1391731-16-0 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,3,9,1,7,3 and 1 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 1391731-16: (9*1)+(8*3)+(7*9)+(6*1)+(5*7)+(4*3)+(3*1)+(2*1)+(1*6)=160 160 % 10 = 0 So 1391731-16-0 is a valid CAS Registry Number.