2557781 has 2 divisors, whose sum is σ = 2557782. Its totient is φ = 2557780.

The previous prime is 2557777. The next prime is 2557813. The reversal of 2557781 is 1877552.

2557781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1932100 + 625681 = 1390^2 + 791^2 .

It is a cyclic number.

It is not a de Polignac number, because 2557781 - 2² = 2557777 is a prime.

It is a super-2 number, since 2×2557781² = 13084487287922, which contains 22 as substring.

It is a Chen prime.

It is equal to p₁₈₆₉₈₃ and since 2557781 and 186983 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2557741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1278890 + 1278891.

It is an arithmetic number, because the mean of its divisors is an integer number (1278891).

2^2557781 is an apocalyptic number.

It is an amenable number.

2557781 is a deficient number, since it is larger than the sum of its proper divisors (1).

2557781 is an equidigital number, since it uses as much as digits as its factorization.

2557781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 19600, while the sum is 35.

The square root of 2557781 is about 1599.3064121675. The cubic root of 2557781 is about 136.7585389270.

The spelling of 2557781 in words is "two million, five hundred fifty-seven thousand, seven hundred eighty-one".