The CAS Registry Mumber 147666-43-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,4,7,6,6 and 6 respectively; the second part has 2 digits, 4 and 3 respectively. Calculate Digit Verification of CAS Registry Number 147666-43: (8*1)+(7*4)+(6*7)+(5*6)+(4*6)+(3*6)+(2*4)+(1*3)=161 161 % 10 = 1 So 147666-43-1 is a valid CAS Registry Number.