The CAS Registry Mumber 77211-35-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,2,1 and 1 respectively; the second part has 2 digits, 3 and 5 respectively. Calculate Digit Verification of CAS Registry Number 77211-35: (7*7)+(6*7)+(5*2)+(4*1)+(3*1)+(2*3)+(1*5)=119 119 % 10 = 9 So 77211-35-9 is a valid CAS Registry Number.