How many synapses in the average human brain?
The human neocortex contains approximately 1.5x10^14 synapses, connecting its 19–23 billion neurons.

Source: Pakkenberg, B., Pelvig, D., Marner, L., Bundgaard, M. J., Gundersen, H. J. G., Nyengaard, J. R., &amp; Regeur, L. (2003). Aging and the human neocortex. Experimental Gerontology, 38(1-2), 95-99. doi:10.1016/S0531-5565(02)00151-1