The CAS Registry Mumber 126179-09-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,6,1,7 and 9 respectively; the second part has 2 digits, 0 and 9 respectively. Calculate Digit Verification of CAS Registry Number 126179-09: (8*1)+(7*2)+(6*6)+(5*1)+(4*7)+(3*9)+(2*0)+(1*9)=127 127 % 10 = 7 So 126179-09-7 is a valid CAS Registry Number.