256978691 has 2 divisors, whose sum is σ = 256978692. Its totient is φ = 256978690.

The previous prime is 256978679. The next prime is 256978703. The reversal of 256978691 is 196879652.

256978691 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a balanced prime because it is at equal distance from previous prime (256978679) and next prime (256978703).

It is a cyclic number.

It is not a de Polignac number, because 256978691 - 2¹⁰ = 256977667 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (256978391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128489345 + 128489346.

It is an arithmetic number, because the mean of its divisors is an integer number (128489346).

Almost surely, 2^256978691 is an apocalyptic number.

256978691 is a deficient number, since it is larger than the sum of its proper divisors (1).

256978691 is an equidigital number, since it uses as much as digits as its factorization.

256978691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1632960, while the sum is 53.

The square root of 256978691 is about 16030.5549186546. The cubic root of 256978691 is about 635.7685455469.

The spelling of 256978691 in words is "two hundred fifty-six million, nine hundred seventy-eight thousand, six hundred ninety-one".