The CAS Registry Mumber 54855-16-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,4,8,5 and 5 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 54855-16: (7*5)+(6*4)+(5*8)+(4*5)+(3*5)+(2*1)+(1*6)=142 142 % 10 = 2 So 54855-16-2 is a valid CAS Registry Number.