The CAS Registry Mumber 98810-72-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,8,8,1 and 0 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 98810-72: (7*9)+(6*8)+(5*8)+(4*1)+(3*0)+(2*7)+(1*2)=171 171 % 10 = 1 So 98810-72-1 is a valid CAS Registry Number.