The CAS Registry Mumber 1365535-18-7 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,3,6,5,5,3 and 5 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 1365535-18: (9*1)+(8*3)+(7*6)+(6*5)+(5*5)+(4*3)+(3*5)+(2*1)+(1*8)=167 167 % 10 = 7 So 1365535-18-7 is a valid CAS Registry Number.