The CAS Registry Mumber 58928-33-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,8,9,2 and 8 respectively; the second part has 2 digits, 3 and 3 respectively. Calculate Digit Verification of CAS Registry Number 58928-33: (7*5)+(6*8)+(5*9)+(4*2)+(3*8)+(2*3)+(1*3)=169 169 % 10 = 9 So 58928-33-9 is a valid CAS Registry Number.