256390721 has 2 divisors, whose sum is σ = 256390722. Its totient is φ = 256390720.

The previous prime is 256390699. The next prime is 256390777. The reversal of 256390721 is 127093652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 235960321 + 20430400 = 15361^2 + 4520^2 .

It is a cyclic number.

It is not a de Polignac number, because 256390721 - 2¹⁴ = 256374337 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (256395721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128195360 + 128195361.

It is an arithmetic number, because the mean of its divisors is an integer number (128195361).

Almost surely, 2^256390721 is an apocalyptic number.

It is an amenable number.

256390721 is a deficient number, since it is larger than the sum of its proper divisors (1).

256390721 is an equidigital number, since it uses as much as digits as its factorization.

256390721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 22680, while the sum is 35.

The square root of 256390721 is about 16012.2053759000. The cubic root of 256390721 is about 635.2832935219.

The spelling of 256390721 in words is "two hundred fifty-six million, three hundred ninety thousand, seven hundred twenty-one".