The CAS Registry Mumber 6267-81-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,2,6 and 7 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 6267-81: (6*6)+(5*2)+(4*6)+(3*7)+(2*8)+(1*1)=108 108 % 10 = 8 So 6267-81-8 is a valid CAS Registry Number.