1256655561 has 8 divisors (see below), whose sum is σ = 1914903744. Its totient is φ = 718088880.

The previous prime is 1256655539. The next prime is 1256655581. The reversal of 1256655561 is 1655566521.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1256655561 - 2⁵ = 1256655529 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1256655511) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 29920350 + ... + 29920391.

It is an arithmetic number, because the mean of its divisors is an integer number (239362968).

Almost surely, 2^1256655561 is an apocalyptic number.

It is an amenable number.

1256655561 is a deficient number, since it is larger than the sum of its proper divisors (658248183).

1256655561 is an equidigital number, since it uses as much as digits as its factorization.

1256655561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59840751.

The product of its digits is 270000, while the sum is 42.

The square root of 1256655561 is about 35449.3379486839. The cubic root of 1256655561 is about 1079.1258246790.

The spelling of 1256655561 in words is "one billion, two hundred fifty-six million, six hundred fifty-five thousand, five hundred sixty-one".