The CAS Registry Mumber 78718-45-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,8,7,1 and 8 respectively; the second part has 2 digits, 4 and 5 respectively. Calculate Digit Verification of CAS Registry Number 78718-45: (7*7)+(6*8)+(5*7)+(4*1)+(3*8)+(2*4)+(1*5)=173 173 % 10 = 3 So 78718-45-3 is a valid CAS Registry Number.