The CAS Registry Mumber 98670-72-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,8,6,7 and 0 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 98670-72: (7*9)+(6*8)+(5*6)+(4*7)+(3*0)+(2*7)+(1*2)=185 185 % 10 = 5 So 98670-72-5 is a valid CAS Registry Number.