The CAS Registry Mumber 19179-21-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,9,1,7 and 9 respectively; the second part has 2 digits, 2 and 1 respectively. Calculate Digit Verification of CAS Registry Number 19179-21: (7*1)+(6*9)+(5*1)+(4*7)+(3*9)+(2*2)+(1*1)=126 126 % 10 = 6 So 19179-21-6 is a valid CAS Registry Number.