The CAS Registry Mumber 52186-81-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,2,1,8 and 6 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 52186-81: (7*5)+(6*2)+(5*1)+(4*8)+(3*6)+(2*8)+(1*1)=119 119 % 10 = 9 So 52186-81-9 is a valid CAS Registry Number.