Forty-nine is the square of the prime numberseven and hence the fourth non-unitary squareprime of the formp2. Both of its digits are square numbers, 4 being the square of 2 and 9 being the square of 3.
It appears in thePadovan sequence, preceded by the terms 21, 28, 37 (it is the sum of the first two of these).[1]
Along with the number that immediately derives from it, 77, the only number under100 not having itshome prime known (as of 2016[update]).
The smallest triple of three squares in arithmetic succession is (1,25,49), and the second smallest is (49,169,289).
49 and 94 are the only numbers below 100 whose all permutations are composites but they are not multiples of 3, repdigits or numbers which only have digits 0, 2, 4, 5, 6 and 8, even excluding the trivial one digit terms.
There are 42 positive integers less than 49 and coprime to 49. (42 is the period.) Multiplying 020408163265306122448979591836734693877551 by each of these integers results in acyclic permutation of the original number:
During theManhattan Project,plutonium was also often referred to simply as "49". Number 4 was for the last digit in 94 (atomic number of plutonium) and 9 for the last digit in Pu-239, the weapon-grade fissile isotope used in nuclear bombs.[5][6]
A 49 is a party after apowwow or any gathering of American Indians, held by the participants. It is also type of song that is sung on such occasions. A 49 is typically held in an isolated place and features drumming and singing.[7]
