1256256161 has 4 divisors (see below), whose sum is σ = 1265426052. Its totient is φ = 1247086272.

The previous prime is 1256256139. The next prime is 1256256173. The reversal of 1256256161 is 1616526521.

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 817102225 + 439153936 = 28585^2 + 20956^2 .

It is a cyclic number.

It is not a de Polignac number, because 1256256161 - 2³⁰ = 182514337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1256256181) 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, 4584740 + ... + 4585013.

It is an arithmetic number, because the mean of its divisors is an integer number (316356513).

Almost surely, 2^1256256161 is an apocalyptic number.

It is an amenable number.

1256256161 is a deficient number, since it is larger than the sum of its proper divisors (9169891).

1256256161 is an equidigital number, since it uses as much as digits as its factorization.

1256256161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9169890.

The product of its digits is 21600, while the sum is 35.

The square root of 1256256161 is about 35443.7041094748. The cubic root of 1256256161 is about 1079.0114871900.

The spelling of 1256256161 in words is "one billion, two hundred fifty-six million, two hundred fifty-six thousand, one hundred sixty-one".