The CAS Registry Mumber 201852-41-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,0,1,8,5 and 2 respectively; the second part has 2 digits, 4 and 1 respectively. Calculate Digit Verification of CAS Registry Number 201852-41: (8*2)+(7*0)+(6*1)+(5*8)+(4*5)+(3*2)+(2*4)+(1*1)=97 97 % 10 = 7 So 201852-41-7 is a valid CAS Registry Number.