6561551655 has 48 divisors (see below), whose sum is σ = 11507358720. Its totient is φ = 3458407104.

The previous prime is 6561551653. The next prime is 6561551657. The reversal of 6561551655 is 5561551656.

6561551655 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (6561551653) and next prime (6561551657).

It is not a de Polignac number, because 6561551655 - 2¹ = 6561551653 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 6561551655.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6561551651) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2867922 + ... + 2870208.

It is an arithmetic number, because the mean of its divisors is an integer number (239736640).

Almost surely, 2^6561551655 is an apocalyptic number.

6561551655 is a deficient number, since it is larger than the sum of its proper divisors (4945807065).

6561551655 is a wasteful number, since it uses less digits than its factorization.

6561551655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3020 (or 3017 counting only the distinct ones).

The product of its digits is 675000, while the sum is 45.

The square root of 6561551655 is about 81003.4052062011. The cubic root of 6561551655 is about 1872.1279078927.

Subtracting from 6561551655 its reverse (5561551656), we obtain a palindrome (999999999).

The spelling of 6561551655 in words is "six billion, five hundred sixty-one million, five hundred fifty-one thousand, six hundred fifty-five".