The CAS Registry Mumber 4280-12-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,2,8 and 0 respectively; the second part has 2 digits, 1 and 2 respectively. Calculate Digit Verification of CAS Registry Number 4280-12: (6*4)+(5*2)+(4*8)+(3*0)+(2*1)+(1*2)=70 70 % 10 = 0 So 4280-12-0 is a valid CAS Registry Number.