The CAS Registry Mumber 125917-89-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,5,9,1 and 7 respectively; the second part has 2 digits, 8 and 9 respectively. Calculate Digit Verification of CAS Registry Number 125917-89: (8*1)+(7*2)+(6*5)+(5*9)+(4*1)+(3*7)+(2*8)+(1*9)=147 147 % 10 = 7 So 125917-89-7 is a valid CAS Registry Number.