The CAS Registry Mumber 126647-11-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,6,6,4 and 7 respectively; the second part has 2 digits, 1 and 1 respectively. Calculate Digit Verification of CAS Registry Number 126647-11: (8*1)+(7*2)+(6*6)+(5*6)+(4*4)+(3*7)+(2*1)+(1*1)=128 128 % 10 = 8 So 126647-11-8 is a valid CAS Registry Number.