The CAS Registry Mumber 6694-96-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,6,9 and 4 respectively; the second part has 2 digits, 9 and 6 respectively. Calculate Digit Verification of CAS Registry Number 6694-96: (6*6)+(5*6)+(4*9)+(3*4)+(2*9)+(1*6)=138 138 % 10 = 8 So 6694-96-8 is a valid CAS Registry Number.