a large/a big number

[user_gary]

I have a large number of pen.
I have a big number of pen.

Are these two sentences correct?
Please help me.

[Harry Smith]

I have a large number of pen.
I have a big number of pen.

Are these two sentences correct?
Please help me.

Not pen but pens.
I'd say: I have a large number of pens.

[user_gary]

Thank you Harry Smith.
I also say "a large number of" only. But I wonder if I can say "a big number of" as the word big also has the same meaning "large in amount".

[Harry Smith]

Thank you Harry Smith.
I also say "a large number of" only. But I wonder if I can say "a big number of" as the word big also has the same meaning "large in amount".

I think you can say "a big number of" too, as there is no special rule.