It is a Jordan-Polya number, since it can be written as 6! ⋅ (3!)2 ⋅ 2!.
It is a tau number, because it is divible by the number of its divisors (80).
It is a nialpdrome in base 16.
It is an unprimeable number.
251840 is an apocalyptic number.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 51840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (92565).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
51840 is an equidigital number, since it uses as much as digits as its factorization.
51840 is an odious number, because the sum of its binary digits is odd.
The square root of 51840 is about 227.6839915321. The cubic root of 51840 is about 37.2867900714.
Multiplying 51840 by its product of nonzero digits (160), we get a square (8294400 = 28802).
51840 divided by its product of nonzero digits (160) gives a square (324 = 182).
The spelling of 51840 in words is "fifty-one thousand, eight hundred forty".