The CAS Registry Mumber 143221-26-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,4,3,2,2 and 1 respectively; the second part has 2 digits, 2 and 6 respectively. Calculate Digit Verification of CAS Registry Number 143221-26: (8*1)+(7*4)+(6*3)+(5*2)+(4*2)+(3*1)+(2*2)+(1*6)=85 85 % 10 = 5 So 143221-26-5 is a valid CAS Registry Number.