153

The number 153 is associated with the geometric shape known as the Vesica piscis or Mandorla. Archimedes, in his Measurement of a Circle, referred to this ratio (153/265), as constituting the "measure of the fish", this ratio being an imperfect representation of 1 / 3 ≈ 0.57735 {\displaystyle 1/{\sqrt {3}}\approx 0.57735}. As a triangular number, 153 is the sum of the first 17 integers, and is also the sum of the first five positive factorials: 1 ! + 2 ! + 3 ! + 4 ! + 5 ! {\displaystyle 1!+2!+3!+4!+5!}.