The CAS Registry Mumber 76016-21-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,6,0,1 and 6 respectively; the second part has 2 digits, 2 and 1 respectively. Calculate Digit Verification of CAS Registry Number 76016-21: (7*7)+(6*6)+(5*0)+(4*1)+(3*6)+(2*2)+(1*1)=112 112 % 10 = 2 So 76016-21-2 is a valid CAS Registry Number.