5681821 has 4 divisors (see below), whose sum is σ = 5820444. Its totient is φ = 5543200.

The previous prime is 5681803. The next prime is 5681861. The reversal of 5681821 is 1281865.

5681821 = 1685² + 1686².

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2842596 + 2839225 = 1686^2 + 1685^2 .

It is not a de Polignac number, because 5681821 - 2⁷ = 5681693 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (5681861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 69250 + ... + 69331.

It is an arithmetic number, because the mean of its divisors is an integer number (1455111).

Almost surely, 2^5681821 is an apocalyptic number.

5681821 is the 1686-th centered square number.

It is an amenable number.

5681821 is a deficient number, since it is larger than the sum of its proper divisors (138623).

5681821 is a wasteful number, since it uses less digits than its factorization.

5681821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138622.

The product of its digits is 3840, while the sum is 31.

The square root of 5681821 is about 2383.6570642607. The cubic root of 5681821 is about 178.4414933782.

The spelling of 5681821 in words is "five million, six hundred eighty-one thousand, eight hundred twenty-one".