55820 has 12 divisors (see below), whose sum is σ = 117264. Its totient is φ = 22320.

The previous prime is 55819. The next prime is 55823. The reversal of 55820 is 2855.

55820 = 80² + 81² + ... + 87².

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 2791 = 55820 / (5 + 5 + 8 + 2 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 55792 and 55801.

It is not an unprimeable number, because it can be changed into a prime (55823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1376 + ... + 1415.

It is an arithmetic number, because the mean of its divisors is an integer number (9772).

2⁵⁵⁸²⁰ is an apocalyptic number.

It is an amenable number.

55820 is an abundant number, since it is smaller than the sum of its proper divisors (61444).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (58632).

55820 is a wasteful number, since it uses less digits than its factorization.

55820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2800 (or 2798 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 55820 is about 236.2625658034. The cubic root of 55820 is about 38.2175882750.

The spelling of 55820 in words is "fifty-five thousand, eight hundred twenty".