The CAS Registry Mumber 1609545-55-2 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,6,0,9,5,4 and 5 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 1609545-55: (9*1)+(8*6)+(7*0)+(6*9)+(5*5)+(4*4)+(3*5)+(2*5)+(1*5)=182 182 % 10 = 2 So 1609545-55-2 is a valid CAS Registry Number.