6561105491 has 4 divisors (see below), whose sum is σ = 6561462552. Its totient is φ = 6560748432.

The previous prime is 6561105487. The next prime is 6561105521. The reversal of 6561105491 is 1945011656.

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 6561105491 - 2² = 6561105487 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6561105431) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 149381 + ... + 188246.

It is an arithmetic number, because the mean of its divisors is an integer number (1640365638).

Almost surely, 2^6561105491 is an apocalyptic number.

6561105491 is a deficient number, since it is larger than the sum of its proper divisors (357061).

6561105491 is a wasteful number, since it uses less digits than its factorization.

6561105491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 357060.

The product of its (nonzero) digits is 32400, while the sum is 38.

The square root of 6561105491 is about 81000.6511763949. The cubic root of 6561105491 is about 1872.0854740776.

The spelling of 6561105491 in words is "six billion, five hundred sixty-one million, one hundred five thousand, four hundred ninety-one".