257561021 has 2 divisors, whose sum is σ = 257561022. Its totient is φ = 257561020.

The previous prime is 257561011. The next prime is 257561047. The reversal of 257561021 is 120165752.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 253255396 + 4305625 = 15914^2 + 2075^2 .

It is a cyclic number.

It is not a de Polignac number, because 257561021 - 2²² = 253366717 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (257561011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128780510 + 128780511.

It is an arithmetic number, because the mean of its divisors is an integer number (128780511).

Almost surely, 2^257561021 is an apocalyptic number.

It is an amenable number.

257561021 is a deficient number, since it is larger than the sum of its proper divisors (1).

257561021 is an equidigital number, since it uses as much as digits as its factorization.

257561021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4200, while the sum is 29.

The square root of 257561021 is about 16048.7077672939. The cubic root of 257561021 is about 636.2484138640.

The spelling of 257561021 in words is "two hundred fifty-seven million, five hundred sixty-one thousand, twenty-one".