6664221 has 16 divisors (see below), whose sum is σ = 10454400. Its totient is φ = 4181184.

The previous prime is 6664213. The next prime is 6664223. The reversal of 6664221 is 1224666.

It is a happy number.

It is not a de Polignac number, because 6664221 - 2³ = 6664213 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6664223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6801 + ... + 7718.

It is an arithmetic number, because the mean of its divisors is an integer number (653400).

Almost surely, 2^6664221 is an apocalyptic number.

It is an amenable number.

6664221 is a deficient number, since it is larger than the sum of its proper divisors (3790179).

6664221 is a wasteful number, since it uses less digits than its factorization.

6664221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14545 (or 14539 counting only the distinct ones).

The product of its digits is 3456, while the sum is 27.

The square root of 6664221 is about 2581.5152527150. The cubic root of 6664221 is about 188.1841883568.

Adding to 6664221 its reverse (1224666), we get a palindrome (7888887).

The spelling of 6664221 in words is "six million, six hundred sixty-four thousand, two hundred twenty-one".