The CAS Registry Mumber 39728-72-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,9,7,2 and 8 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 39728-72: (7*3)+(6*9)+(5*7)+(4*2)+(3*8)+(2*7)+(1*2)=158 158 % 10 = 8 So 39728-72-8 is a valid CAS Registry Number.