1256566321 has 4 divisors (see below), whose sum is σ = 1266460672. Its totient is φ = 1246671972.

The previous prime is 1256566313. The next prime is 1256566327. The reversal of 1256566321 is 1236656521.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1256566321 - 2³ = 1256566313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1256566327) 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, 4946985 + ... + 4947238.

It is an arithmetic number, because the mean of its divisors is an integer number (316615168).

Almost surely, 2^1256566321 is an apocalyptic number.

It is an amenable number.

1256566321 is a deficient number, since it is larger than the sum of its proper divisors (9894351).

1256566321 is an equidigital number, since it uses as much as digits as its factorization.

1256566321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9894350.

The product of its digits is 64800, while the sum is 37.

The square root of 1256566321 is about 35448.0792286409. The cubic root of 1256566321 is about 1079.1002797667.

The spelling of 1256566321 in words is "one billion, two hundred fifty-six million, five hundred sixty-six thousand, three hundred twenty-one".