The CAS Registry Mumber 73870-98-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,3,8,7 and 0 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 73870-98: (7*7)+(6*3)+(5*8)+(4*7)+(3*0)+(2*9)+(1*8)=161 161 % 10 = 1 So 73870-98-1 is a valid CAS Registry Number.