6660221 has 2 divisors, whose sum is σ = 6660222. Its totient is φ = 6660220.

The previous prime is 6660217. The next prime is 6660233. The reversal of 6660221 is 1220666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6002500 + 657721 = 2450^2 + 811^2 .

It is a cyclic number.

It is not a de Polignac number, because 6660221 - 2² = 6660217 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6660211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3330110 + 3330111.

It is an arithmetic number, because the mean of its divisors is an integer number (3330111).

Almost surely, 2^6660221 is an apocalyptic number.

It is an amenable number.

6660221 is a deficient number, since it is larger than the sum of its proper divisors (1).

6660221 is an equidigital number, since it uses as much as digits as its factorization.

6660221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 6660221 is about 2580.7403976379. The cubic root of 6660221 is about 188.1465301716.

Adding to 6660221 its reverse (1220666), we get a palindrome (7880887).

The spelling of 6660221 in words is "six million, six hundred sixty thousand, two hundred twenty-one".