256621005 has 24 divisors (see below), whose sum is σ = 464151168. Its totient is φ = 130913376.

The previous prime is 256620983. The next prime is 256621073. The reversal of 256621005 is 500126652.

It is not a de Polignac number, because 256621005 - 2⁶ = 256620941 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 256621005.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 122937 + ... + 125006.

It is an arithmetic number, because the mean of its divisors is an integer number (19339632).

Almost surely, 2^256621005 is an apocalyptic number.

It is an amenable number.

256621005 is a deficient number, since it is larger than the sum of its proper divisors (207530163).

256621005 is a wasteful number, since it uses less digits than its factorization.

256621005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247977 (or 247974 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 256621005 is about 16019.3946514842. The cubic root of 256621005 is about 635.4734353485.

Adding to 256621005 its reverse (500126652), we get a palindrome (756747657).

The spelling of 256621005 in words is "two hundred fifty-six million, six hundred twenty-one thousand, five".