The CAS Registry Mumber 7740-58-1 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,7,4 and 0 respectively; the second part has 2 digits, 5 and 8 respectively. Calculate Digit Verification of CAS Registry Number 7740-58: (6*7)+(5*7)+(4*4)+(3*0)+(2*5)+(1*8)=111 111 % 10 = 1 So 7740-58-1 is a valid CAS Registry Number.