The CAS Registry Mumber 15764-83-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,5,7,6 and 4 respectively; the second part has 2 digits, 8 and 3 respectively. Calculate Digit Verification of CAS Registry Number 15764-83: (7*1)+(6*5)+(5*7)+(4*6)+(3*4)+(2*8)+(1*3)=127 127 % 10 = 7 So 15764-83-7 is a valid CAS Registry Number.