6668821 has 2 divisors, whose sum is σ = 6668822. Its totient is φ = 6668820.

The previous prime is 6668807. The next prime is 6668833. The reversal of 6668821 is 1288666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5640625 + 1028196 = 2375^2 + 1014^2 .

It is a cyclic number.

It is not a de Polignac number, because 6668821 - 2⁵ = 6668789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6668861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3334410 + 3334411.

It is an arithmetic number, because the mean of its divisors is an integer number (3334411).

Almost surely, 2^6668821 is an apocalyptic number.

It is an amenable number.

6668821 is a deficient number, since it is larger than the sum of its proper divisors (1).

6668821 is an equidigital number, since it uses as much as digits as its factorization.

6668821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27648, while the sum is 37.

The square root of 6668821 is about 2582.4060486298. The cubic root of 6668821 is about 188.2274766457.

The spelling of 6668821 in words is "six million, six hundred sixty-eight thousand, eight hundred twenty-one".