256640105 has 4 divisors (see below), whose sum is σ = 307968132. Its totient is φ = 205312080.

The previous prime is 256640093. The next prime is 256640107. The reversal of 256640105 is 501046652.

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

It can be written as a sum of positive squares in 2 ways, for example, as 124367104 + 132273001 = 11152^2 + 11501^2 .

It is not a de Polignac number, because 256640105 - 2⁸ = 256639849 is a prime.

It is a super-2 number, since 2×256640105² = 131728286988822050, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (256640107) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25664006 + ... + 25664015.

It is an arithmetic number, because the mean of its divisors is an integer number (76992033).

Almost surely, 2^256640105 is an apocalyptic number.

It is an amenable number.

256640105 is a deficient number, since it is larger than the sum of its proper divisors (51328027).

256640105 is an equidigital number, since it uses as much as digits as its factorization.

256640105 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51328026.

The product of its (nonzero) digits is 7200, while the sum is 29.

The square root of 256640105 is about 16019.9907927564. The cubic root of 256640105 is about 635.4892008045.

Adding to 256640105 its reverse (501046652), we get a palindrome (757686757).

The spelling of 256640105 in words is "two hundred fifty-six million, six hundred forty thousand, one hundred five".