256440661 has 2 divisors, whose sum is σ = 256440662. Its totient is φ = 256440660.

The previous prime is 256440643. The next prime is 256440671. The reversal of 256440661 is 166044652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 173976100 + 82464561 = 13190^2 + 9081^2 .

It is a cyclic number.

It is not a de Polignac number, because 256440661 - 2¹³ = 256432469 is a prime.

It is a super-2 number, since 2×256440661² = 131523625228233842, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256440671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128220330 + 128220331.

It is an arithmetic number, because the mean of its divisors is an integer number (128220331).

Almost surely, 2^256440661 is an apocalyptic number.

It is an amenable number.

256440661 is a deficient number, since it is larger than the sum of its proper divisors (1).

256440661 is an equidigital number, since it uses as much as digits as its factorization.

256440661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34560, while the sum is 34.

The square root of 256440661 is about 16013.7647353769. The cubic root of 256440661 is about 635.3245378486.

The spelling of 256440661 in words is "two hundred fifty-six million, four hundred forty thousand, six hundred sixty-one".