The CAS Registry Mumber 21312-49-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,1,3,1 and 2 respectively; the second part has 2 digits, 4 and 9 respectively. Calculate Digit Verification of CAS Registry Number 21312-49: (7*2)+(6*1)+(5*3)+(4*1)+(3*2)+(2*4)+(1*9)=62 62 % 10 = 2 So 21312-49-2 is a valid CAS Registry Number.