257820721 has 2 divisors, whose sum is σ = 257820722. Its totient is φ = 257820720.

The previous prime is 257820713. The next prime is 257820763. The reversal of 257820721 is 127028752.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 213744400 + 44076321 = 14620^2 + 6639^2 .

It is a cyclic number.

It is not a de Polignac number, because 257820721 - 2³ = 257820713 is a prime.

It is not a weakly prime, because it can be changed into another prime (257820421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128910360 + 128910361.

It is an arithmetic number, because the mean of its divisors is an integer number (128910361).

Almost surely, 2^257820721 is an apocalyptic number.

It is an amenable number.

257820721 is a deficient number, since it is larger than the sum of its proper divisors (1).

257820721 is an equidigital number, since it uses as much as digits as its factorization.

257820721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15680, while the sum is 34.

The square root of 257820721 is about 16056.7967228834. The cubic root of 257820721 is about 636.4621861295.

The spelling of 257820721 in words is "two hundred fifty-seven million, eight hundred twenty thousand, seven hundred twenty-one".