The CAS Registry Mumber 6481-98-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,4,8 and 1 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 6481-98: (6*6)+(5*4)+(4*8)+(3*1)+(2*9)+(1*8)=117 117 % 10 = 7 So 6481-98-7 is a valid CAS Registry Number.