The CAS Registry Mumber 89844-20-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,9,8,4 and 4 respectively; the second part has 2 digits, 2 and 0 respectively. Calculate Digit Verification of CAS Registry Number 89844-20: (7*8)+(6*9)+(5*8)+(4*4)+(3*4)+(2*2)+(1*0)=182 182 % 10 = 2 So 89844-20-2 is a valid CAS Registry Number.