The CAS Registry Mumber 73763-18-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,3,7,6 and 3 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 73763-18: (7*7)+(6*3)+(5*7)+(4*6)+(3*3)+(2*1)+(1*8)=145 145 % 10 = 5 So 73763-18-5 is a valid CAS Registry Number.