257721216 has 64 divisors (see below), whose sum is σ = 692355600. Its totient is φ = 84930560.

The previous prime is 257721209. The next prime is 257721221. The reversal of 257721216 is 612127752.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30406 + ... + 37946.

Almost surely, 2^257721216 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 257721216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (346177800).

257721216 is an abundant number, since it is smaller than the sum of its proper divisors (434634384).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

257721216 is an equidigital number, since it uses as much as digits as its factorization.

257721216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7647 (or 7635 counting only the distinct ones).

The product of its digits is 11760, while the sum is 33.

The square root of 257721216 is about 16053.6978917631. The cubic root of 257721216 is about 636.3802954798.

Adding to 257721216 its reverse (612127752), we get a palindrome (869848968).

The spelling of 257721216 in words is "two hundred fifty-seven million, seven hundred twenty-one thousand, two hundred sixteen".