6561665 has 16 divisors (see below), whose sum is σ = 8755776. Its totient is φ = 4680000.

The previous prime is 6561649. The next prime is 6561673. The reversal of 6561665 is 5661656.

It is not a de Polignac number, because 6561665 - 2⁴ = 6561649 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1790 + ... + 4040.

It is an arithmetic number, because the mean of its divisors is an integer number (547236).

Almost surely, 2^6561665 is an apocalyptic number.

It is an amenable number.

6561665 is a deficient number, since it is larger than the sum of its proper divisors (2194111).

6561665 is a wasteful number, since it uses less digits than its factorization.

6561665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2320.

The product of its digits is 32400, while the sum is 35.

The square root of 6561665 is about 2561.5747109932. The cubic root of 6561665 is about 187.2138687615.

Subtracting from 6561665 its reverse (5661656), we obtain a palindrome (900009).

The spelling of 6561665 in words is "six million, five hundred sixty-one thousand, six hundred sixty-five".