The CAS Registry Mumber 87853-55-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,8,5 and 3 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 87853-55: (7*8)+(6*7)+(5*8)+(4*5)+(3*3)+(2*5)+(1*5)=182 182 % 10 = 2 So 87853-55-2 is a valid CAS Registry Number.