The CAS Registry Mumber 125023-40-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,5,0,2 and 3 respectively; the second part has 2 digits, 4 and 0 respectively. Calculate Digit Verification of CAS Registry Number 125023-40: (8*1)+(7*2)+(6*5)+(5*0)+(4*2)+(3*3)+(2*4)+(1*0)=77 77 % 10 = 7 So 125023-40-7 is a valid CAS Registry Number.