256318021 has 4 divisors (see below), whose sum is σ = 256351392. Its totient is φ = 256284652.

The previous prime is 256318009. The next prime is 256318039. The reversal of 256318021 is 120813652.

256318021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256318021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256318091) 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, 1296 + ... + 22678.

It is an arithmetic number, because the mean of its divisors is an integer number (64087848).

Almost surely, 2^256318021 is an apocalyptic number.

It is an amenable number.

256318021 is a deficient number, since it is larger than the sum of its proper divisors (33371).

256318021 is a wasteful number, since it uses less digits than its factorization.

256318021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33370.

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 256318021 is about 16009.9350716984. The cubic root of 256318021 is about 635.2232426469.

It can be divided in two parts, 2563180 and 21, that added together give a square (2563201 = 1601²).

The spelling of 256318021 in words is "two hundred fifty-six million, three hundred eighteen thousand, twenty-one".