145 (number)

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.<ref>Template:Cite web</ref>
145 is a pentagonal number<ref>Template:Cite web</ref> and a centered square number.<ref>Template:Cite web</ref>
<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 3⁴ + 4³, making it a Leyland number.
<math>145 = 1! + 4! + 5!</math>, making it a factorion.<ref name=":0">Template:Cite web</ref> The only other numbers that have this property are 1, 2 and 40585.<ref name=":0" />
<math>145=5^2+5!=11^2+4!=12^2+1!</math>, making 145 the smallest number that can be written as the sum of a square number and a factorial in 3 ways. The next number with this property is 46249.<ref>Template:Cite web</ref>