56821 has 2 divisors, whose sum is σ = 56822. Its totient is φ = 56820.

The previous prime is 56813. The next prime is 56827. The reversal of 56821 is 12865.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 45796 + 11025 = 214^2 + 105^2 .

It is a cyclic number.

It is not a de Polignac number, because 56821 - 2³ = 56813 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 56792 and 56801.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (56827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 28410 + 28411.

It is an arithmetic number, because the mean of its divisors is an integer number (28411).

2⁵⁶⁸²¹ is an apocalyptic number.

It is an amenable number.

56821 is a deficient number, since it is larger than the sum of its proper divisors (1).

56821 is an equidigital number, since it uses as much as digits as its factorization.

56821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 480, while the sum is 22.

The square root of 56821 is about 238.3715587062. The cubic root of 56821 is about 38.4446835892. Note that the first 3 decimals are identical.

Subtracting from 56821 its reverse (12865), we obtain a triangular number (43956 = T₂₉₆).

The spelling of 56821 in words is "fifty-six thousand, eight hundred twenty-one".