The CAS Registry Mumber 18759-78-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,7,5 and 9 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 18759-78: (7*1)+(6*8)+(5*7)+(4*5)+(3*9)+(2*7)+(1*8)=159 159 % 10 = 9 So 18759-78-9 is a valid CAS Registry Number.