"rounding" issue with large number using BandMath

Description

Issue reported on the forum.

When using the BandMath application, the large numbers are truncated.

Steps to reproduce

Try using parameter -exp "im1b1*100000 + im2b1" where im1b1 is smaller that 10000.

Configuration information

Tested on Linux, with OTB version 6.7 & 7.2 & 7.3.