The CAS Registry Mumber 87271-64-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,2,7 and 1 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 87271-64: (7*8)+(6*7)+(5*2)+(4*7)+(3*1)+(2*6)+(1*4)=155 155 % 10 = 5 So 87271-64-5 is a valid CAS Registry Number.