The CAS Registry Mumber 80249-90-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,2,4 and 9 respectively; the second part has 2 digits, 9 and 0 respectively. Calculate Digit Verification of CAS Registry Number 80249-90: (7*8)+(6*0)+(5*2)+(4*4)+(3*9)+(2*9)+(1*0)=127 127 % 10 = 7 So 80249-90-7 is a valid CAS Registry Number.