The CAS Registry Mumber 97879-13-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,7,8,7 and 9 respectively; the second part has 2 digits, 1 and 3 respectively. Calculate Digit Verification of CAS Registry Number 97879-13: (7*9)+(6*7)+(5*8)+(4*7)+(3*9)+(2*1)+(1*3)=205 205 % 10 = 5 So 97879-13-5 is a valid CAS Registry Number.