Optimization for number to idle game notation display function?

This function's purpose is to replace a big number, 1405789042927 for example, with "1.40T", I came up with this code after realising that a huge if statement wouldn't be viable for this, the problem is that it looks kinda expensive and the game started lagging a bit after the latest scripts, this function is in my Utils static class and gets called everytime i need to update a TMP text. What are your thoughts on this?

 static string notationAtlas = "K M B T Qa Qi Sx Sp Oc No Dc Ud Dd Td Qad Qid Sxd Spd Od Nd V Uv Dv Tv Qav Qiv Sxv Spv Ov Nv Tt";
 static string[] notation = notationAtlas.Split(' ');

 public static string IdleGameNumberBigDouble(BigDouble number)
 {
     if (number < 1000) return BigDouble.Round(number) + "";

     for (int i = 1; i < notation.Length + 1; i++)
     {
         if (number < Mathf.Pow(1000, i+1))
         {
             return (number / Mathf.Pow(1000, i)).ToString("F2") + notation[i-1];
         }
     }
     return (number / Mathf.Pow(1000, notation.Length + 1)).ToString("F2") + "Max";
 }