The CAS Registry Mumber 76716-18-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,6,7,1 and 6 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 76716-18: (7*7)+(6*6)+(5*7)+(4*1)+(3*6)+(2*1)+(1*8)=152 152 % 10 = 2 So 76716-18-2 is a valid CAS Registry Number.