257821247 has 4 divisors (see below), whose sum is σ = 260479296. Its totient is φ = 255163200.

The previous prime is 257821211. The next prime is 257821261. The reversal of 257821247 is 742128752.

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

It is a cyclic number.

It is not a de Polignac number, because 257821247 - 2¹⁰ = 257820223 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 257821247.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (257827247) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1328879 + ... + 1329072.

It is an arithmetic number, because the mean of its divisors is an integer number (65119824).

Almost surely, 2^257821247 is an apocalyptic number.

257821247 is a deficient number, since it is larger than the sum of its proper divisors (2658049).

257821247 is an equidigital number, since it uses as much as digits as its factorization.

257821247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2658048.

The product of its digits is 62720, while the sum is 38.

The square root of 257821247 is about 16056.8131022317. The cubic root of 257821247 is about 636.4626189611.

Adding to 257821247 its reverse (742128752), we get a palindrome (999949999).

The spelling of 257821247 in words is "two hundred fifty-seven million, eight hundred twenty-one thousand, two hundred forty-seven".