The CAS Registry Mumber 50978-31-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,0,9,7 and 8 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 50978-31: (7*5)+(6*0)+(5*9)+(4*7)+(3*8)+(2*3)+(1*1)=139 139 % 10 = 9 So 50978-31-9 is a valid CAS Registry Number.