The CAS Registry Mumber 7180-58-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,1,8 and 0 respectively; the second part has 2 digits, 5 and 8 respectively. Calculate Digit Verification of CAS Registry Number 7180-58: (6*7)+(5*1)+(4*8)+(3*0)+(2*5)+(1*8)=97 97 % 10 = 7 So 7180-58-7 is a valid CAS Registry Number.