55821 has 8 divisors (see below), whose sum is σ = 77760. Its totient is φ = 35552.

The previous prime is 55819. The next prime is 55823. The reversal of 55821 is 12855.

55821 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (55819) and next prime (55823).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 55821 - 2¹ = 55819 is a prime.

It is a congruent number.

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

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 336 + ... + 473.

It is an arithmetic number, because the mean of its divisors is an integer number (9720).

2⁵⁵⁸²¹ is an apocalyptic number.

It is an amenable number.

55821 is a deficient number, since it is larger than the sum of its proper divisors (21939).

55821 is a wasteful number, since it uses less digits than its factorization.

55821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 835.

The product of its digits is 400, while the sum is 21.

The square root of 55821 is about 236.2646820835. The cubic root of 55821 is about 38.2178164929.

The spelling of 55821 in words is "fifty-five thousand, eight hundred twenty-one".