The CAS Registry Mumber 57381-15-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,7,3,8 and 1 respectively; the second part has 2 digits, 1 and 5 respectively. Calculate Digit Verification of CAS Registry Number 57381-15: (7*5)+(6*7)+(5*3)+(4*8)+(3*1)+(2*1)+(1*5)=134 134 % 10 = 4 So 57381-15-4 is a valid CAS Registry Number.