The CAS Registry Mumber 80372-54-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,3,7 and 2 respectively; the second part has 2 digits, 5 and 4 respectively. Calculate Digit Verification of CAS Registry Number 80372-54: (7*8)+(6*0)+(5*3)+(4*7)+(3*2)+(2*5)+(1*4)=119 119 % 10 = 9 So 80372-54-9 is a valid CAS Registry Number.