6561729576865 has 4 divisors (see below), whose sum is σ = 7874075492244. Its totient is φ = 5249383661488.

The previous prime is 6561729576851. The next prime is 6561729576887. The reversal of 6561729576865 is 5686759271656.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 679945369744 + 5881784207121 = 824588^2 + 2425239^2 .

It is a cyclic number.

It is not a de Polignac number, because 6561729576865 - 2²⁹ = 6561192705953 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 656172957682 + ... + 656172957691.

It is an arithmetic number, because the mean of its divisors is an integer number (1968518873061).

Almost surely, 2^{6561729576865} is an apocalyptic number.

It is an amenable number.

6561729576865 is a deficient number, since it is larger than the sum of its proper divisors (1312345915379).

6561729576865 is a wasteful number, since it uses less digits than its factorization.

6561729576865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1312345915378.

The product of its digits is 1143072000, while the sum is 73.

The spelling of 6561729576865 in words is "six trillion, five hundred sixty-one billion, seven hundred twenty-nine million, five hundred seventy-six thousand, eight hundred sixty-five".