256831387 has 2 divisors, whose sum is σ = 256831388. Its totient is φ = 256831386.

The previous prime is 256831369. The next prime is 256831391. The reversal of 256831387 is 783138652.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256831387 is a prime.

It is a super-2 number, since 2×256831387² = 131924722696687538, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (256834387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128415693 + 128415694.

It is an arithmetic number, because the mean of its divisors is an integer number (128415694).

Almost surely, 2^256831387 is an apocalyptic number.

256831387 is a deficient number, since it is larger than the sum of its proper divisors (1).

256831387 is an equidigital number, since it uses as much as digits as its factorization.

256831387 is an evil number, because the sum of its binary digits is even.

The product of its digits is 241920, while the sum is 43.

The square root of 256831387 is about 16025.9597840504. The cubic root of 256831387 is about 635.6470450063.

The spelling of 256831387 in words is "two hundred fifty-six million, eight hundred thirty-one thousand, three hundred eighty-seven".