The CAS Registry Mumber 403-59-8 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 4,0 and 3 respectively; the second part has 2 digits, 5 and 9 respectively. Calculate Digit Verification of CAS Registry Number 403-59: (5*4)+(4*0)+(3*3)+(2*5)+(1*9)=48 48 % 10 = 8 So 403-59-8 is a valid CAS Registry Number.