The CAS Registry Mumber 3657-04-3 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,6,5 and 7 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 3657-04: (6*3)+(5*6)+(4*5)+(3*7)+(2*0)+(1*4)=93 93 % 10 = 3 So 3657-04-3 is a valid CAS Registry Number.