Excel trick,find common digit between two number in two different cells

I have 7899 in A1 and 567 in B2

in E1 I am getting the mode 7

the formula is

=MODE(VALUE(MID(A1,ROW(INDIRECT("1:"&LEN(A1))),1)),VALUE(MID(B1,ROW(INDIRECT("1:"&LEN(B1))),1)))

it's an array formula so you have to use ctrl+shift+enter