The CAS Registry Mumber 77605-18-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,6,0 and 5 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 77605-18: (7*7)+(6*7)+(5*6)+(4*0)+(3*5)+(2*1)+(1*8)=146 146 % 10 = 6 So 77605-18-6 is a valid CAS Registry Number.