6681821 has 4 divisors (see below), whose sum is σ = 6693792. Its totient is φ = 6669852.

The previous prime is 6681817. The next prime is 6681839. The reversal of 6681821 is 1281866.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1281866 = 2 ⋅640933.

It is a cyclic number.

It is not a de Polignac number, because 6681821 - 2² = 6681817 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6681421) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5105 + ... + 6278.

It is an arithmetic number, because the mean of its divisors is an integer number (1673448).

Almost surely, 2^6681821 is an apocalyptic number.

It is an amenable number.

6681821 is a deficient number, since it is larger than the sum of its proper divisors (11971).

6681821 is a wasteful number, since it uses less digits than its factorization.

6681821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11970.

The product of its digits is 4608, while the sum is 32.

The square root of 6681821 is about 2584.9218556854. The cubic root of 6681821 is about 188.3497055928.

The spelling of 6681821 in words is "six million, six hundred eighty-one thousand, eight hundred twenty-one".