6645681 has 24 divisors (see below), whose sum is σ = 11271104. Its totient is φ = 3693600.

The previous prime is 6645679. The next prime is 6645697. The reversal of 6645681 is 1865466.

6645681 is a `hidden beast` number, since 6 + 645 + 6 + 8 + 1 = 666.

It is not a de Polignac number, because 6645681 - 2¹ = 6645679 is a prime.

It is a super-2 number, since 2×6645681² = 88330151907522, which contains 22 as substring.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6645601) 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 23 ways as a sum of consecutive naturals, for example, 906 + ... + 3756.

Almost surely, 2^6645681 is an apocalyptic number.

It is an amenable number.

6645681 is a deficient number, since it is larger than the sum of its proper divisors (4625423).

6645681 is a wasteful number, since it uses less digits than its factorization.

6645681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2901 (or 2898 counting only the distinct ones).

The product of its digits is 34560, while the sum is 36.

The square root of 6645681 is about 2577.9218374497. The cubic root of 6645681 is about 188.0095155135.

The spelling of 6645681 in words is "six million, six hundred forty-five thousand, six hundred eighty-one".