256218135688261 has 2 divisors, whose sum is σ = 256218135688262. Its totient is φ = 256218135688260.

The previous prime is 256218135688259. The next prime is 256218135688301. The reversal of 256218135688261 is 162886531812652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 224488640873025 + 31729494815236 = 14982945^2 + 5632894^2 .

It is a cyclic number.

It is not a de Polignac number, because 256218135688261 - 2¹ = 256218135688259 is a prime.

Together with 256218135688259, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 256218135688193 and 256218135688202.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256218135689261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128109067844130 + 128109067844131.

It is an arithmetic number, because the mean of its divisors is an integer number (128109067844131).

Almost surely, 2^{256218135688261} is an apocalyptic number.

It is an amenable number.

256218135688261 is a deficient number, since it is larger than the sum of its proper divisors (1).

256218135688261 is an equidigital number, since it uses as much as digits as its factorization.

256218135688261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 66355200, while the sum is 64.

The spelling of 256218135688261 in words is "two hundred fifty-six trillion, two hundred eighteen billion, one hundred thirty-five million, six hundred eighty-eight thousand, two hundred sixty-one".