6856721 has 4 divisors (see below), whose sum is σ = 6868452. Its totient is φ = 6844992.

The previous prime is 6856697. The next prime is 6856723. The reversal of 6856721 is 1276586.

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 96721 + 6760000 = 311^2 + 2600^2 .

It is a cyclic number.

It is not a de Polignac number, because 6856721 - 2¹⁰ = 6855697 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (6856723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4940 + ... + 6173.

It is an arithmetic number, because the mean of its divisors is an integer number (1717113).

Almost surely, 2^6856721 is an apocalyptic number.

It is an amenable number.

6856721 is a deficient number, since it is larger than the sum of its proper divisors (11731).

6856721 is a wasteful number, since it uses less digits than its factorization.

6856721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11730.

The product of its digits is 20160, while the sum is 35.

The square root of 6856721 is about 2618.5341319143. The cubic root of 6856721 is about 189.9789542709.

The spelling of 6856721 in words is "six million, eight hundred fifty-six thousand, seven hundred twenty-one".