6643655 has 4 divisors (see below), whose sum is σ = 7972392. Its totient is φ = 5314920.

The previous prime is 6643649. The next prime is 6643667. The reversal of 6643655 is 5563466.

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

It is a de Polignac number, because none of the positive numbers 2^k-6643655 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 664361 + ... + 664370.

It is an arithmetic number, because the mean of its divisors is an integer number (1993098).

Almost surely, 2^6643655 is an apocalyptic number.

6643655 is a deficient number, since it is larger than the sum of its proper divisors (1328737).

6643655 is a wasteful number, since it uses less digits than its factorization.

6643655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1328736.

The product of its digits is 64800, while the sum is 35.

The square root of 6643655 is about 2577.5288553186. The cubic root of 6643655 is about 187.9904080665.

The spelling of 6643655 in words is "six million, six hundred forty-three thousand, six hundred fifty-five".