The CAS Registry Mumber 57242-36-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,7,2,4 and 2 respectively; the second part has 2 digits, 3 and 6 respectively. Calculate Digit Verification of CAS Registry Number 57242-36: (7*5)+(6*7)+(5*2)+(4*4)+(3*2)+(2*3)+(1*6)=121 121 % 10 = 1 So 57242-36-1 is a valid CAS Registry Number.