The CAS Registry Mumber 97507-33-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,7,5,0 and 7 respectively; the second part has 2 digits, 3 and 3 respectively. Calculate Digit Verification of CAS Registry Number 97507-33: (7*9)+(6*7)+(5*5)+(4*0)+(3*7)+(2*3)+(1*3)=160 160 % 10 = 0 So 97507-33-0 is a valid CAS Registry Number.