6561331655 has 16 divisors (see below), whose sum is σ = 8291155680. Its totient is φ = 4970904192.

The previous prime is 6561331643. The next prime is 6561331657. The reversal of 6561331655 is 5561331656.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 6561331655 - 2¹⁰ = 6561330631 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6561331657) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 269237 + ... + 292593.

It is an arithmetic number, because the mean of its divisors is an integer number (518197230).

Almost surely, 2^6561331655 is an apocalyptic number.

6561331655 is a deficient number, since it is larger than the sum of its proper divisors (1729824025).

6561331655 is a wasteful number, since it uses less digits than its factorization.

6561331655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26338.

The product of its digits is 243000, while the sum is 41.

The square root of 6561331655 is about 81002.0472272152. The cubic root of 6561331655 is about 1872.1069843487.

Subtracting from 6561331655 its reverse (5561331656), we obtain a palindrome (999999999).

The spelling of 6561331655 in words is "six billion, five hundred sixty-one million, three hundred thirty-one thousand, six hundred fifty-five".