2781565 has 4 divisors (see below), whose sum is σ = 3337884. Its totient is φ = 2225248.

The previous prime is 2781521. The next prime is 2781577. The reversal of 2781565 is 5651872.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 784996 + 1996569 = 886^2 + 1413^2 .

It is a cyclic number.

It is not a de Polignac number, because 2781565 - 2¹⁷ = 2650493 is a prime.

It is a Duffinian number.

2781565 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 2781565.

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 278152 + ... + 278161.

It is an arithmetic number, because the mean of its divisors is an integer number (834471).

2^2781565 is an apocalyptic number.

It is an amenable number.

2781565 is a deficient number, since it is larger than the sum of its proper divisors (556319).

2781565 is an equidigital number, since it uses as much as digits as its factorization.

2781565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 556318.

The product of its digits is 16800, while the sum is 34.

The square root of 2781565 is about 1667.8024463347. The cubic root of 2781565 is about 140.6359672105.

The spelling of 2781565 in words is "two million, seven hundred eighty-one thousand, five hundred sixty-five".