The CAS Registry Mumber 65145-31-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,5,1,4 and 5 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 65145-31: (7*6)+(6*5)+(5*1)+(4*4)+(3*5)+(2*3)+(1*1)=115 115 % 10 = 5 So 65145-31-5 is a valid CAS Registry Number.