The CAS Registry Mumber 16270-74-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,6,2,7 and 0 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 16270-74: (7*1)+(6*6)+(5*2)+(4*7)+(3*0)+(2*7)+(1*4)=99 99 % 10 = 9 So 16270-74-9 is a valid CAS Registry Number.