2128781 has 2 divisors, whose sum is σ = 2128782. Its totient is φ = 2128780.

The previous prime is 2128769. The next prime is 2128783. The reversal of 2128781 is 1878212.

2128781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2128681 + 100 = 1459^2 + 10^2 .

It is a cyclic number.

It is not a de Polignac number, because 2128781 - 2¹⁰ = 2127757 is a prime.

It is a super-2 number, since 2×2128781² = 9063417091922, which contains 22 as substring.

Together with 2128783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2128783) 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, 1064390 + 1064391.

It is an arithmetic number, because the mean of its divisors is an integer number (1064391).

2^2128781 is an apocalyptic number.

2128781 is the 653-rd centered decagonal number.

It is an amenable number.

2128781 is a deficient number, since it is larger than the sum of its proper divisors (1).

2128781 is an equidigital number, since it uses as much as digits as its factorization.

2128781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1792, while the sum is 29.

The square root of 2128781 is about 1459.0342696455. The cubic root of 2128781 is about 128.6402854567.

The spelling of 2128781 in words is "two million, one hundred twenty-eight thousand, seven hundred eighty-one".