256186781 has 2 divisors, whose sum is σ = 256186782. Its totient is φ = 256186780.

The previous prime is 256186771. The next prime is 256186793. The reversal of 256186781 is 187681652.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 223981156 + 32205625 = 14966^2 + 5675^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256186781 is a prime.

It is a super-2 number, since 2×256186781² = 131263333518283922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256186741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128093390 + 128093391.

It is an arithmetic number, because the mean of its divisors is an integer number (128093391).

Almost surely, 2^256186781 is an apocalyptic number.

It is an amenable number.

256186781 is a deficient number, since it is larger than the sum of its proper divisors (1).

256186781 is an equidigital number, since it uses as much as digits as its factorization.

256186781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 161280, while the sum is 44.

The square root of 256186781 is about 16005.8358419671. The cubic root of 256186781 is about 635.1148084310.

The spelling of 256186781 in words is "two hundred fifty-six million, one hundred eighty-six thousand, seven hundred eighty-one".