256521663 has 6 divisors (see below), whose sum is σ = 370531304. Its totient is φ = 171014436.

The previous prime is 256521659. The next prime is 256521673. The reversal of 256521663 is 366125652.

It is a happy number.

It is not a de Polignac number, because 256521663 - 2² = 256521659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256521673) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 14251195 + ... + 14251212.

Almost surely, 2^256521663 is an apocalyptic number.

256521663 is a deficient number, since it is larger than the sum of its proper divisors (114009641).

256521663 is a wasteful number, since it uses less digits than its factorization.

256521663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28502413 (or 28502410 counting only the distinct ones).

The product of its digits is 64800, while the sum is 36.

The square root of 256521663 is about 16016.2936723825. The cubic root of 256521663 is about 635.3914242003.

The spelling of 256521663 in words is "two hundred fifty-six million, five hundred twenty-one thousand, six hundred sixty-three".