The CAS Registry Mumber 157870-43-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,5,7,8,7 and 0 respectively; the second part has 2 digits, 4 and 3 respectively. Calculate Digit Verification of CAS Registry Number 157870-43: (8*1)+(7*5)+(6*7)+(5*8)+(4*7)+(3*0)+(2*4)+(1*3)=164 164 % 10 = 4 So 157870-43-4 is a valid CAS Registry Number.