The CAS Registry Mumber 407-76-1 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 4,0 and 7 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 407-76: (5*4)+(4*0)+(3*7)+(2*7)+(1*6)=61 61 % 10 = 1 So 407-76-1 is a valid CAS Registry Number.