The CAS Registry Mumber 12158-59-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,2,1,5 and 8 respectively; the second part has 2 digits, 5 and 9 respectively. Calculate Digit Verification of CAS Registry Number 12158-59: (7*1)+(6*2)+(5*1)+(4*5)+(3*8)+(2*5)+(1*9)=87 87 % 10 = 7 So 12158-59-7 is a valid CAS Registry Number.