The CAS Registry Mumber 17853-12-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,7,8,5 and 3 respectively; the second part has 2 digits, 1 and 2 respectively. Calculate Digit Verification of CAS Registry Number 17853-12: (7*1)+(6*7)+(5*8)+(4*5)+(3*3)+(2*1)+(1*2)=122 122 % 10 = 2 So 17853-12-2 is a valid CAS Registry Number.