The CAS Registry Mumber 57699-51-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,7,6,9 and 9 respectively; the second part has 2 digits, 5 and 1 respectively. Calculate Digit Verification of CAS Registry Number 57699-51: (7*5)+(6*7)+(5*6)+(4*9)+(3*9)+(2*5)+(1*1)=181 181 % 10 = 1 So 57699-51-1 is a valid CAS Registry Number.