The CAS Registry Mumber 87168-47-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,1,6 and 8 respectively; the second part has 2 digits, 4 and 7 respectively. Calculate Digit Verification of CAS Registry Number 87168-47: (7*8)+(6*7)+(5*1)+(4*6)+(3*8)+(2*4)+(1*7)=166 166 % 10 = 6 So 87168-47-6 is a valid CAS Registry Number.