The CAS Registry Mumber 154013-21-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,5,4,0,1 and 3 respectively; the second part has 2 digits, 2 and 1 respectively. Calculate Digit Verification of CAS Registry Number 154013-21: (8*1)+(7*5)+(6*4)+(5*0)+(4*1)+(3*3)+(2*2)+(1*1)=85 85 % 10 = 5 So 154013-21-5 is a valid CAS Registry Number.