The CAS Registry Mumber 4352-09-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,3,5 and 2 respectively; the second part has 2 digits, 0 and 9 respectively. Calculate Digit Verification of CAS Registry Number 4352-09: (6*4)+(5*3)+(4*5)+(3*2)+(2*0)+(1*9)=74 74 % 10 = 4 So 4352-09-4 is a valid CAS Registry Number.