The CAS Registry Mumber 4823-98-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,8,2 and 3 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 4823-98: (6*4)+(5*8)+(4*2)+(3*3)+(2*9)+(1*8)=107 107 % 10 = 7 So 4823-98-7 is a valid CAS Registry Number.