The CAS Registry Mumber 18758-41-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,7,5 and 8 respectively; the second part has 2 digits, 4 and 1 respectively. Calculate Digit Verification of CAS Registry Number 18758-41: (7*1)+(6*8)+(5*7)+(4*5)+(3*8)+(2*4)+(1*1)=143 143 % 10 = 3 So 18758-41-3 is a valid CAS Registry Number.