6664821 has 8 divisors (see below), whose sum is σ = 8973120. Its totient is φ = 4399872.

The previous prime is 6664811. The next prime is 6664831. The reversal of 6664821 is 1284666.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (6664811) and next prime (6664831).

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

It is not a de Polignac number, because 6664821 - 2⁵ = 6664789 is a prime.

6664821 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6664811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10476 + ... + 11093.

It is an arithmetic number, because the mean of its divisors is an integer number (1121640).

Almost surely, 2^6664821 is an apocalyptic number.

It is an amenable number.

6664821 is a deficient number, since it is larger than the sum of its proper divisors (2308299).

6664821 is a wasteful number, since it uses less digits than its factorization.

6664821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21675.

The product of its digits is 13824, while the sum is 33.

The square root of 6664821 is about 2581.6314609177. The cubic root of 6664821 is about 188.1898357848.

The spelling of 6664821 in words is "six million, six hundred sixty-four thousand, eight hundred twenty-one".