The CAS Registry Mumber 850851-04-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 8,5,0,8,5 and 1 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 850851-04: (8*8)+(7*5)+(6*0)+(5*8)+(4*5)+(3*1)+(2*0)+(1*4)=166 166 % 10 = 6 So 850851-04-6 is a valid CAS Registry Number.