The CAS Registry Mumber 109879-79-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,9,8,7 and 9 respectively; the second part has 2 digits, 7 and 9 respectively. Calculate Digit Verification of CAS Registry Number 109879-79: (8*1)+(7*0)+(6*9)+(5*8)+(4*7)+(3*9)+(2*7)+(1*9)=180 180 % 10 = 0 So 109879-79-0 is a valid CAS Registry Number.