The CAS Registry Mumber 18857-23-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,8,5 and 7 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 18857-23: (7*1)+(6*8)+(5*8)+(4*5)+(3*7)+(2*2)+(1*3)=143 143 % 10 = 3 So 18857-23-3 is a valid CAS Registry Number.