The CAS Registry Mumber 438-36-8 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 4,3 and 8 respectively; the second part has 2 digits, 3 and 6 respectively. Calculate Digit Verification of CAS Registry Number 438-36: (5*4)+(4*3)+(3*8)+(2*3)+(1*6)=68 68 % 10 = 8 So 438-36-8 is a valid CAS Registry Number.