257821221 has 16 divisors (see below), whose sum is σ = 393096704. Its totient is φ = 147241584.

The previous prime is 257821211. The next prime is 257821261. The reversal of 257821221 is 122128752.

257821221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 257821221 - 2¹¹ = 257819173 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (257821211) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 62406 + ... + 66408.

It is an arithmetic number, because the mean of its divisors is an integer number (24568544).

Almost surely, 2^257821221 is an apocalyptic number.

257821221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

257821221 is a deficient number, since it is larger than the sum of its proper divisors (135275483).

257821221 is a wasteful number, since it uses less digits than its factorization.

257821221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7080.

The product of its digits is 4480, while the sum is 30.

The square root of 257821221 is about 16056.8122926065. The cubic root of 257821221 is about 636.4625975664.

Adding to 257821221 its reverse (122128752), we get a palindrome (379949973).

The spelling of 257821221 in words is "two hundred fifty-seven million, eight hundred twenty-one thousand, two hundred twenty-one".