The CAS Registry Mumber 56983-31-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,6,9,8 and 3 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 56983-31: (7*5)+(6*6)+(5*9)+(4*8)+(3*3)+(2*3)+(1*1)=164 164 % 10 = 4 So 56983-31-4 is a valid CAS Registry Number.