The CAS Registry Mumber 1258543-03-1 includes 10 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 7 digits, 1,2,5,8,5,4 and 3 respectively; the second part has 2 digits, 0 and 3 respectively. Calculate Digit Verification of CAS Registry Number 1258543-03: (9*1)+(8*2)+(7*5)+(6*8)+(5*5)+(4*4)+(3*3)+(2*0)+(1*3)=161 161 % 10 = 1 So 1258543-03-1 is a valid CAS Registry Number.