Change WooCommerce ordernumber prefix

functions.php

add_filter( 'woocommerce_order_number', 'jm_woocommerce_order_number', 1, 2 );
/**
 * Remove # prefix from  WooCommerce Order Number
 * Could also be done with gettext: https://github.com/woothemes/woocommerce/blob/master/includes/abstracts/abstract-wc-order.php#L537
 * 
 */
function jm_woocommerce_order_number( $oldnumber, $order ) {
	return str_replace('#', '', $order->id);
}