256540621 has 2 divisors, whose sum is σ = 256540622. Its totient is φ = 256540620.

The previous prime is 256540619. The next prime is 256540657. The reversal of 256540621 is 126045652.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 197711721 + 58828900 = 14061^2 + 7670^2 .

It is a cyclic number.

It is not a de Polignac number, because 256540621 - 2¹ = 256540619 is a prime.

Together with 256540619, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256540681) 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 as a sum of consecutive naturals, namely, 128270310 + 128270311.

It is an arithmetic number, because the mean of its divisors is an integer number (128270311).

Almost surely, 2^256540621 is an apocalyptic number.

It is an amenable number.

256540621 is a deficient number, since it is larger than the sum of its proper divisors (1).

256540621 is an equidigital number, since it uses as much as digits as its factorization.

256540621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 14400, while the sum is 31.

The square root of 256540621 is about 16016.8854962505. The cubic root of 256540621 is about 635.4070764896.

The spelling of 256540621 in words is "two hundred fifty-six million, five hundred forty thousand, six hundred twenty-one".