The CAS Registry Mumber 57976-42-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,7,9,7 and 6 respectively; the second part has 2 digits, 4 and 2 respectively. Calculate Digit Verification of CAS Registry Number 57976-42: (7*5)+(6*7)+(5*9)+(4*7)+(3*6)+(2*4)+(1*2)=178 178 % 10 = 8 So 57976-42-8 is a valid CAS Registry Number.