6645561 has 16 divisors (see below), whose sum is σ = 9662016. Its totient is φ = 4038336.

The previous prime is 6645557. The next prime is 6645571. The reversal of 6645561 is 1655466.

It is not a de Polignac number, because 6645561 - 2² = 6645557 is a prime.

6645561 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (6645571) 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 15 ways as a sum of consecutive naturals, for example, 2211 + ... + 4263.

It is an arithmetic number, because the mean of its divisors is an integer number (603876).

Almost surely, 2^6645561 is an apocalyptic number.

It is an amenable number.

6645561 is a deficient number, since it is larger than the sum of its proper divisors (3016455).

6645561 is a wasteful number, since it uses less digits than its factorization.

6645561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2152.

The product of its digits is 21600, while the sum is 33.

The square root of 6645561 is about 2577.8985627833. The cubic root of 6645561 is about 188.0083838875.

The spelling of 6645561 in words is "six million, six hundred forty-five thousand, five hundred sixty-one".