How do you write 2003?

'2003'. You SAY: 'el ano dos mil tres'

2003 in roman numeral is MMIII

In 2003 Boeing had to write down a $1.1 billion loss on its Hughes acquisition, $1 billion on Jeppesen-Sanderson, and $1 billion in operational losses.

For example, if you want 2.3 million, which in scientific notation is 2.3 x 106, you simply write 2.3e6.

X-XX-MMIII