The CAS Registry Mumber 89957-43-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,9,9,5 and 7 respectively; the second part has 2 digits, 4 and 3 respectively. Calculate Digit Verification of CAS Registry Number 89957-43: (7*8)+(6*9)+(5*9)+(4*5)+(3*7)+(2*4)+(1*3)=207 207 % 10 = 7 So 89957-43-7 is a valid CAS Registry Number.