256821751 has 4 divisors (see below), whose sum is σ = 256854712. Its totient is φ = 256788792.

The previous prime is 256821743. The next prime is 256821769. The reversal of 256821751 is 157128652.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 256821751 - 2³ = 256821743 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 256821751.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256821731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2476 + ... + 22798.

It is an arithmetic number, because the mean of its divisors is an integer number (64213678).

Almost surely, 2^256821751 is an apocalyptic number.

256821751 is a deficient number, since it is larger than the sum of its proper divisors (32961).

256821751 is a wasteful number, since it uses less digits than its factorization.

256821751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32960.

The product of its digits is 33600, while the sum is 37.

The square root of 256821751 is about 16025.6591440103. The cubic root of 256821751 is about 635.6390953399.

The spelling of 256821751 in words is "two hundred fifty-six million, eight hundred twenty-one thousand, seven hundred fifty-one".