The CAS Registry Mumber 93638-93-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,3,6,3 and 8 respectively; the second part has 2 digits, 9 and 3 respectively. Calculate Digit Verification of CAS Registry Number 93638-93: (7*9)+(6*3)+(5*6)+(4*3)+(3*8)+(2*9)+(1*3)=168 168 % 10 = 8 So 93638-93-8 is a valid CAS Registry Number.