The CAS Registry Mumber 29966-04-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,9,9,6 and 6 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 29966-04: (7*2)+(6*9)+(5*9)+(4*6)+(3*6)+(2*0)+(1*4)=159 159 % 10 = 9 So 29966-04-9 is a valid CAS Registry Number.