6551821 has 2 divisors, whose sum is σ = 6551822. Its totient is φ = 6551820.

The previous prime is 6551801. The next prime is 6551833. The reversal of 6551821 is 1281556.

6551821 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 4622500 + 1929321 = 2150^2 + 1389^2 .

It is a cyclic number.

It is not a de Polignac number, because 6551821 - 2⁷ = 6551693 is a prime.

6551821 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 6551821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6551801) by changing a digit.

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

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3275910 + 3275911.

It is an arithmetic number, because the mean of its divisors is an integer number (3275911).

Almost surely, 2^6551821 is an apocalyptic number.

It is an amenable number.

6551821 is a deficient number, since it is larger than the sum of its proper divisors (1).

6551821 is an equidigital number, since it uses as much as digits as its factorization.

6551821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2400, while the sum is 28.

The square root of 6551821 is about 2559.6525154794. The cubic root of 6551821 is about 187.1202006808.

The spelling of 6551821 in words is "six million, five hundred fifty-one thousand, eight hundred twenty-one".