The CAS Registry Mumber 3312-27-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,3,1 and 2 respectively; the second part has 2 digits, 2 and 7 respectively. Calculate Digit Verification of CAS Registry Number 3312-27: (6*3)+(5*3)+(4*1)+(3*2)+(2*2)+(1*7)=54 54 % 10 = 4 So 3312-27-4 is a valid CAS Registry Number.