6666821 has 8 divisors (see below), whose sum is σ = 7641600. Its totient is φ = 5697648.

The previous prime is 6666797. The next prime is 6666833. The reversal of 6666821 is 1286666.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 6666821 - 2¹⁰ = 6665797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6666841) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1580 + ... + 3978.

It is an arithmetic number, because the mean of its divisors is an integer number (955200).

Almost surely, 2^6666821 is an apocalyptic number.

It is an amenable number.

6666821 is a deficient number, since it is larger than the sum of its proper divisors (974779).

6666821 is a wasteful number, since it uses less digits than its factorization.

6666821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2803.

The product of its digits is 20736, while the sum is 35.

The square root of 6666821 is about 2582.0187838201. The cubic root of 6666821 is about 188.2086580973.

The spelling of 6666821 in words is "six million, six hundred sixty-six thousand, eight hundred twenty-one".