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

• 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.^[1]
• 145 is a pentagonal number^[2] and a centered square number.^[3]
• . 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.
• , making it a factorion.^[4] The only other numbers that have this property are 1, 2 and 40585.^[4]
• , 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.^[5]

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

• The Natural Number 145
• Parker, Matt. "145 and the Melancoil". Numberphile. Brady Haran. Archived from the original on 2013-05-14. Retrieved 2013-04-06.