One in
how many? Pick a thing that probably won't happen. Every dot below is one of the outcomes that could have happened instead. Exactly one of them is you.

Grain size follows the Wentworth grade scale (medium sand, 0.5 mm); packing follows random close packing at ~62% — Song, Wang & Makse, Nature 2008. The pile settles by the falling-sand rule — straight down if it can, otherwise off the shoulder — which is what produces an angle of repose.