2557821 has 12 divisors (see below), whose sum is σ = 3908832. Its totient is φ = 1457424.

The previous prime is 2557817. The next prime is 2557823. The reversal of 2557821 is 1287552.

It is not a de Polignac number, because 2557821 - 2² = 2557817 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2557823) 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 in 11 ways as a sum of consecutive naturals, for example, 7155 + ... + 7503.

It is an arithmetic number, because the mean of its divisors is an integer number (325736).

2^2557821 is an apocalyptic number.

2557821 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

2557821 is a deficient number, since it is larger than the sum of its proper divisors (1351011).

2557821 is an frugal number, since it uses more digits than its factorization.

2557821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 708 (or 359 counting only the distinct ones).

The product of its digits is 5600, while the sum is 30.

The square root of 2557821 is about 1599.3189175396. The cubic root of 2557821 is about 136.7592518252.

The spelling of 2557821 in words is "two million, five hundred fifty-seven thousand, eight hundred twenty-one".