6561591 has 4 divisors (see below), whose sum is σ = 8748792. Its totient is φ = 4374392.

The previous prime is 6561589. The next prime is 6561613. The reversal of 6561591 is 1951656.

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 6561591 - 2¹ = 6561589 is a prime.

It is an Ulam number.

It is a D-number.

6561591 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6561521) 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, 1093596 + ... + 1093601.

It is an arithmetic number, because the mean of its divisors is an integer number (2187198).

Almost surely, 2^6561591 is an apocalyptic number.

6561591 is a deficient number, since it is larger than the sum of its proper divisors (2187201).

6561591 is a wasteful number, since it uses less digits than its factorization.

6561591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2187200.

The product of its digits is 8100, while the sum is 33.

The square root of 6561591 is about 2561.5602667125. The cubic root of 6561591 is about 187.2131649829.

The spelling of 6561591 in words is "six million, five hundred sixty-one thousand, five hundred ninety-one".