The CAS Registry Mumber 6104-98-9 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,1,0 and 4 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 6104-98: (6*6)+(5*1)+(4*0)+(3*4)+(2*9)+(1*8)=79 79 % 10 = 9 So 6104-98-9 is a valid CAS Registry Number.