145

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. 145 = 12 2 + 1 2 = 8 2 + 9 2 {\displaystyle 145=12^{2}+1^{2}=8^{2}+9^{2}}. 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.