The CAS Registry Mumber 63688-97-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,3,6,8 and 8 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 63688-97: (7*6)+(6*3)+(5*6)+(4*8)+(3*8)+(2*9)+(1*7)=171 171 % 10 = 1 So 63688-97-1 is a valid CAS Registry Number.