The CAS Registry Mumber 12351-40-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,2,3,5 and 1 respectively; the second part has 2 digits, 4 and 0 respectively. Calculate Digit Verification of CAS Registry Number 12351-40: (7*1)+(6*2)+(5*3)+(4*5)+(3*1)+(2*4)+(1*0)=65 65 % 10 = 5 So 12351-40-5 is a valid CAS Registry Number.