The CAS Registry Mumber 78818-27-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,8,8,1 and 8 respectively; the second part has 2 digits, 2 and 7 respectively. Calculate Digit Verification of CAS Registry Number 78818-27: (7*7)+(6*8)+(5*8)+(4*1)+(3*8)+(2*2)+(1*7)=176 176 % 10 = 6 So 78818-27-6 is a valid CAS Registry Number.