The CAS Registry Mumber 20942-32-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,0,9,4 and 2 respectively; the second part has 2 digits, 3 and 2 respectively. Calculate Digit Verification of CAS Registry Number 20942-32: (7*2)+(6*0)+(5*9)+(4*4)+(3*2)+(2*3)+(1*2)=89 89 % 10 = 9 So 20942-32-9 is a valid CAS Registry Number.