6561660601555 has 4 divisors (see below), whose sum is σ = 7873992721872. Its totient is φ = 5249328481240.

The previous prime is 6561660601523. The next prime is 6561660601567. The reversal of 6561660601555 is 5551060661656.

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

It is not a de Polignac number, because 6561660601555 - 2⁵ = 6561660601523 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 656166060151 + ... + 656166060160.

It is an arithmetic number, because the mean of its divisors is an integer number (1968498180468).

Almost surely, 2^{6561660601555} is an apocalyptic number.

6561660601555 is a deficient number, since it is larger than the sum of its proper divisors (1312332120317).

6561660601555 is a wasteful number, since it uses less digits than its factorization.

6561660601555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1312332120316.

The product of its (nonzero) digits is 4860000, while the sum is 52.

The spelling of 6561660601555 in words is "six trillion, five hundred sixty-one billion, six hundred sixty million, six hundred one thousand, five hundred fifty-five".