The CAS Registry Mumber 15210-66-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,5,2,1 and 0 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 15210-66: (7*1)+(6*5)+(5*2)+(4*1)+(3*0)+(2*6)+(1*6)=69 69 % 10 = 9 So 15210-66-9 is a valid CAS Registry Number.