The CAS Registry Mumber 79698-66-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,9,6,9 and 8 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 79698-66: (7*7)+(6*9)+(5*6)+(4*9)+(3*8)+(2*6)+(1*6)=211 211 % 10 = 1 So 79698-66-1 is a valid CAS Registry Number.