The CAS Registry Mumber 432551-43-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 4,3,2,5,5 and 1 respectively; the second part has 2 digits, 4 and 3 respectively. Calculate Digit Verification of CAS Registry Number 432551-43: (8*4)+(7*3)+(6*2)+(5*5)+(4*5)+(3*1)+(2*4)+(1*3)=124 124 % 10 = 4 So 432551-43-4 is a valid CAS Registry Number.