256551 has 4 divisors (see below), whose sum is σ = 342072. Its totient is φ = 171032.

The previous prime is 256541. The next prime is 256561. The reversal of 256551 is 155652.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (256541) and next prime (256561).

It is a cyclic number.

It is not a de Polignac number, because 256551 - 2⁷ = 256423 is a prime.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 42756 + ... + 42761.

It is an arithmetic number, because the mean of its divisors is an integer number (85518).

2²⁵⁶⁵⁵¹ is an apocalyptic number.

256551 is a deficient number, since it is larger than the sum of its proper divisors (85521).

256551 is an equidigital number, since it uses as much as digits as its factorization.

256551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 85520.

The product of its digits is 1500, while the sum is 24.

The square root of 256551 is about 506.5086376361. The cubic root of 256551 is about 63.5415645374.

The spelling of 256551 in words is "two hundred fifty-six thousand, five hundred fifty-one".