6664521 has 4 divisors (see below), whose sum is σ = 8886032. Its totient is φ = 4443012.

The previous prime is 6664517. The next prime is 6664523. The reversal of 6664521 is 1254666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 6664521 - 2² = 6664517 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6664523) 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 3 ways as a sum of consecutive naturals, for example, 1110751 + ... + 1110756.

It is an arithmetic number, because the mean of its divisors is an integer number (2221508).

Almost surely, 2^6664521 is an apocalyptic number.

It is an amenable number.

6664521 is a deficient number, since it is larger than the sum of its proper divisors (2221511).

6664521 is a wasteful number, since it uses less digits than its factorization.

6664521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2221510.

The product of its digits is 8640, while the sum is 30.

The square root of 6664521 is about 2581.5733574702. The cubic root of 6664521 is about 188.1870121132.

It can be divided in two parts, 66645 and 21, that added together give a palindrome (66666).

The spelling of 6664521 in words is "six million, six hundred sixty-four thousand, five hundred twenty-one".