The CAS Registry Mumber 1167-42-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,1,6 and 7 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 1167-42: (6*1)+(5*1)+(4*6)+(3*7)+(2*4)+(1*2)=66 66 % 10 = 6 So 1167-42-6 is a valid CAS Registry Number.