The CAS Registry Mumber 7535-16-2 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,5,3 and 5 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 7535-16: (6*7)+(5*5)+(4*3)+(3*5)+(2*1)+(1*6)=102 102 % 10 = 2 So 7535-16-2 is a valid CAS Registry Number.