6645399 has 4 divisors (see below), whose sum is σ = 8860536. Its totient is φ = 4430264.

The previous prime is 6645391. The next prime is 6645461. The reversal of 6645399 is 9935466.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 6645399 - 2³ = 6645391 is a prime.

It is a super-2 number, since 2×6645399² = 88322655738402, which contains 22 as substring.

It is a D-number.

It is a self number, because there is not a number n which added to its sum of digits gives 6645399.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6645391) 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 3 ways as a sum of consecutive naturals, for example, 1107564 + ... + 1107569.

It is an arithmetic number, because the mean of its divisors is an integer number (2215134).

Almost surely, 2^6645399 is an apocalyptic number.

6645399 is a deficient number, since it is larger than the sum of its proper divisors (2215137).

6645399 is a wasteful number, since it uses less digits than its factorization.

6645399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2215136.

The product of its digits is 174960, while the sum is 42.

The square root of 6645399 is about 2577.8671416502. The cubic root of 6645399 is about 188.0068561707.

The spelling of 6645399 in words is "six million, six hundred forty-five thousand, three hundred ninety-nine".