The CAS Registry Mumber 18971-70-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,9,7 and 1 respectively; the second part has 2 digits, 7 and 0 respectively. Calculate Digit Verification of CAS Registry Number 18971-70: (7*1)+(6*8)+(5*9)+(4*7)+(3*1)+(2*7)+(1*0)=145 145 % 10 = 5 So 18971-70-5 is a valid CAS Registry Number.