256643 has 2 divisors, whose sum is σ = 256644. Its totient is φ = 256642.

The previous prime is 256639. The next prime is 256651. The reversal of 256643 is 346652.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 256643 - 2² = 256639 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (256603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128321 + 128322.

It is an arithmetic number, because the mean of its divisors is an integer number (128322).

2²⁵⁶⁶⁴³ is an apocalyptic number.

256643 is a deficient number, since it is larger than the sum of its proper divisors (1).

256643 is an equidigital number, since it uses as much as digits as its factorization.

256643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 26.

The square root of 256643 is about 506.5994472954. The cubic root of 256643 is about 63.5491590317.

Subtracting 256643 from its reverse (346652), we obtain a palindrome (90009).

The spelling of 256643 in words is "two hundred fifty-six thousand, six hundred forty-three".