The CAS Registry Mumber 16562-68-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,6,5,6 and 2 respectively; the second part has 2 digits, 6 and 8 respectively. Calculate Digit Verification of CAS Registry Number 16562-68: (7*1)+(6*6)+(5*5)+(4*6)+(3*2)+(2*6)+(1*8)=118 118 % 10 = 8 So 16562-68-8 is a valid CAS Registry Number.