The CAS Registry Mumber 78694-18-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,8,6,9 and 4 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 78694-18: (7*7)+(6*8)+(5*6)+(4*9)+(3*4)+(2*1)+(1*8)=185 185 % 10 = 5 So 78694-18-5 is a valid CAS Registry Number.