256521013 has 4 divisors (see below), whose sum is σ = 293166880. Its totient is φ = 219875148.

The previous prime is 256521011. The next prime is 256521017. The reversal of 256521013 is 310125652.

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 256521013 - 2¹ = 256521011 is a prime.

It is a super-2 number, since 2×256521013² = 131606060221092338, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256521011) 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, 18322923 + ... + 18322936.

It is an arithmetic number, because the mean of its divisors is an integer number (73291720).

Almost surely, 2^256521013 is an apocalyptic number.

It is an amenable number.

256521013 is a deficient number, since it is larger than the sum of its proper divisors (36645867).

256521013 is an equidigital number, since it uses as much as digits as its factorization.

256521013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36645866.

The product of its (nonzero) digits is 1800, while the sum is 25.

The square root of 256521013 is about 16016.2733805339. The cubic root of 256521013 is about 635.3908875272.

Adding to 256521013 its reverse (310125652), we get a palindrome (566646665).

The spelling of 256521013 in words is "two hundred fifty-six million, five hundred twenty-one thousand, thirteen".