'format' problem

Dear R experts,

  format(12345678, digits = 2)

gives
  [1] "1.2e+07"

while
  format(1234567, digits = 2)

gives
  [1] "1234567"

but I'd like the last number to be represented as "1.2e+06" string too.

Where am I wrong?

Thanks,
Timur.