In standard form it would be 2,603,102. In expanded form it would be 2,000,000+600,000+3,000+100+2.
Bolts are usually classified in terms of two types of measurements: the metric system and the imperial system. In calipers, the metric system is in units of millimeters, while the imperial system is in units of inches. For example, when a bolt is sized as 12 × 1.25 in the metric system, that means the bolt thread diameter measures 12 mm, and the thread pitch measures 1.25 mm.
So, if your metric bolt measures 0.78 over the threads, that means that the
size of the bolt is 0.78 mm in thread pitch. The attached picture shows how you measure the thread pitch.
The median is 42, the lower is 36, and the upper is 86