The CAS Registry Mumber 74111-77-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,1,1 and 1 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 74111-77: (7*7)+(6*4)+(5*1)+(4*1)+(3*1)+(2*7)+(1*7)=106 106 % 10 = 6 So 74111-77-6 is a valid CAS Registry Number.