The CAS Registry Mumber 68117-64-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,8,1,1 and 7 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 68117-64: (7*6)+(6*8)+(5*1)+(4*1)+(3*7)+(2*6)+(1*4)=136 136 % 10 = 6 So 68117-64-6 is a valid CAS Registry Number.