Correct spelling

at least

Correct spelling, explanation: this spelling is the correct one as at least (sometimes at the least) isn’t one word but an expression. This phrase is written separately and means that something is at its lowest possible number. Writing these two words together is a mistake, so atleast is incorrect.

Definition of at least:
1. phrase, at the lowest number, quantity or the poorest quality of something
We need at least 5 people for the team.
2. phrase, anyway, in spite of disadvantages
You could at least give it a try!


Incorrect spelling

atleast

Incorrect spelling, explanation: the correct form, at least is an expression made from two separate words, and it also should be written separately. Atleast is therefore incorrect as at is here a preposition and least meaning lowest level of something.