145 (one hundred [and] forty-five) is the natural number following 144 and preceding 146.

In mathematics

  • Although composite, 145 is a Fermat pseudoprime in sixteen bases with b < 145. In four of those bases, it is a strong pseudoprime: 1, 12, 17, and 144.
  • The Mertens function returns 0.
  • 145 is a pentagonal number and a centered square number.
  • <math>145 = 12^2 + 1^2 = 8^2 + 9^2</math>. 145 is the fourth number that is the sum of two different pairs of squares. Also, 145 is the result of 3<sup>4</sup> + 4<sup>3</sup>, making it a Leyland number.
  • <math>145 = 1! + 4! + 5!</math>, making it a factorion. The only other numbers that have this property are 1, 2 and 40585.

References

  • Wells, D. The Penguin Dictionary of Curious and Interesting Numbers London: Penguin Group. (1987): 140
  • The Natural Number 145