The CAS Registry Mumber 6548-12-5 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,5,4 and 8 respectively; the second part has 2 digits, 1 and 2 respectively. Calculate Digit Verification of CAS Registry Number 6548-12: (6*6)+(5*5)+(4*4)+(3*8)+(2*1)+(1*2)=105 105 % 10 = 5 So 6548-12-5 is a valid CAS Registry Number.