256940009 has 2 divisors, whose sum is σ = 256940010. Its totient is φ = 256940008.

The previous prime is 256939999. The next prime is 256940017. The reversal of 256940009 is 900049652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 240715225 + 16224784 = 15515^2 + 4028^2 .

It is a cyclic number.

It is not a de Polignac number, because 256940009 - 2⁴ = 256939993 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (256940039) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128470004 + 128470005.

It is an arithmetic number, because the mean of its divisors is an integer number (128470005).

Almost surely, 2^256940009 is an apocalyptic number.

It is an amenable number.

256940009 is a deficient number, since it is larger than the sum of its proper divisors (1).

256940009 is an equidigital number, since it uses as much as digits as its factorization.

256940009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19440, while the sum is 35.

The square root of 256940009 is about 16029.3483647964. The cubic root of 256940009 is about 635.7366440264.

The spelling of 256940009 in words is "two hundred fifty-six million, nine hundred forty thousand, nine".