Relativistic effects in element 137 (Feinmanium) and above Here I saw that if an element above atomic no 137 has to exist, it must have electron speed greater than speed of light. My question is , has this calculation  been done keeping in mind Einstein's relativity? {I am just asking, I have not done this calculation.}
Yes, the value 137 occurs even considering Einstein's theory of special relativity.  

137 comes from considering Sommerfeld or Dirac relativistic theories, when the nucleus is modeled as a point.

See equation 1 of A new method for solving the Z > 137 problem and for determination of energy levels of hydrogen-like atoms