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if the last digit of a number is 2 or 8, its square ends in an even digit followed by a 4; if the last digit of a number is 3 or 7, its square ends in an even digit followed by a 9; if the last digit of a number is 4 or 6, its square ends in an odd digit followed by a 6; and; if the last digit of a number is 5, its square ends in 25.
Every even perfect number ends in 6 or 28, base ten; and, with the only exception of 6, ends in 1 in base 9. [55] [56] Therefore, in particular the digital root of every even perfect number other than 6 is 1. The only square-free perfect number is 6. [57]
In their book, Kathleen Ollerenshaw and David S. Brée give a method of construction and enumeration of all most-perfect magic squares. They also show that there is a one-to-one correspondence between reversible squares and most-perfect magic squares. For n = 36, there are about 2.7 × 10 44 essentially different most-perfect magic squares.
[7] [8] [9] It is widely believed, [10] but not proven, that no odd perfect numbers exist; numerous restrictive conditions have been proven, [10] including a lower bound of 10 1500. [11] The following is a list of all 52 currently known (as of January 2025) Mersenne primes and corresponding perfect numbers, along with their exponents p.
A list of articles about numbers (not about numerals). Topics include powers of ten, notable integers, prime and cardinal numbers, and the myriad system.
According to Guy, Erdős has asked whether there are infinitely many pairs of consecutive powerful numbers such as (23 3, 2 3 3 2 13 2) in which neither number in the pair is a square. Walker (1976) showed that there are indeed infinitely many such pairs by showing that 3 3 c 2 + 1 = 7 3 d 2 has infinitely many solutions.
The stock market will have a strong year. The Russell 2000 small-cap index underperformed the S&P 500 by 15 percentage points. This came close to happening at one point, with the average 30-year ...
This method requires memorization of the squares of the one-digit numbers 1 to 9. The square of mn, mn being a two-digit integer, can be calculated as 10 × m(mn + n) + n 2. Meaning the square of mn can be found by adding n to mn, multiplied by m, adding 0 to the end and finally adding the square of n. For example, 23 2: 23 2 = 10 × 2(23 + 3 ...