The CAS Registry Mumber 10409-58-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,0,4,0 and 9 respectively; the second part has 2 digits, 5 and 8 respectively. Calculate Digit Verification of CAS Registry Number 10409-58: (7*1)+(6*0)+(5*4)+(4*0)+(3*9)+(2*5)+(1*8)=72 72 % 10 = 2 So 10409-58-2 is a valid CAS Registry Number.