The CAS Registry Mumber 1220-44-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,2,2 and 0 respectively; the second part has 2 digits, 4 and 4 respectively. Calculate Digit Verification of CAS Registry Number 1220-44: (6*1)+(5*2)+(4*2)+(3*0)+(2*4)+(1*4)=36 36 % 10 = 6 So 1220-44-6 is a valid CAS Registry Number.