The CAS Registry Mumber 745783-73-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 7,4,5,7,8 and 3 respectively; the second part has 2 digits, 7 and 3 respectively. Calculate Digit Verification of CAS Registry Number 745783-73: (8*7)+(7*4)+(6*5)+(5*7)+(4*8)+(3*3)+(2*7)+(1*3)=207 207 % 10 = 7 So 745783-73-7 is a valid CAS Registry Number.