The CAS Registry Mumber 344421-76-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 3,4,4,4,2 and 1 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 344421-76: (8*3)+(7*4)+(6*4)+(5*4)+(4*2)+(3*1)+(2*7)+(1*6)=127 127 % 10 = 7 So 344421-76-7 is a valid CAS Registry Number.