51240 has 64 divisors (see below), whose sum is σ = 178560. Its totient is φ = 11520.

The previous prime is 51239. The next prime is 51241. The reversal of 51240 is 4215.

It is an interprime number because it is at equal distance from previous prime (51239) and next prime (51241).

It is a Harshad number since it is a multiple of its sum of digits (12).

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (51241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 810 + ... + 870.

It is an arithmetic number, because the mean of its divisors is an integer number (2790).

2⁵¹²⁴⁰ 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 51240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (89280).

51240 is an abundant number, since it is smaller than the sum of its proper divisors (127320).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

51240 is a wasteful number, since it uses less digits than its factorization.

51240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82 (or 78 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 12.

The square root of 51240 is about 226.3625410707. The cubic root of 51240 is about 37.1423781285.

Adding to 51240 its reverse (4215), we get a palindrome (55455).

The spelling of 51240 in words is "fifty-one thousand, two hundred forty".