The CAS Registry Mumber 77270-38-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,2,7 and 0 respectively; the second part has 2 digits, 3 and 8 respectively. Calculate Digit Verification of CAS Registry Number 77270-38: (7*7)+(6*7)+(5*2)+(4*7)+(3*0)+(2*3)+(1*8)=143 143 % 10 = 3 So 77270-38-3 is a valid CAS Registry Number.