2809781 has 12 divisors (see below), whose sum is σ = 3146052. Its totient is φ = 2494464.

The previous prime is 2809769. The next prime is 2809783. The reversal of 2809781 is 1879082.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 70756 + 2739025 = 266^2 + 1655^2 .

It is not a de Polignac number, because 2809781 - 2⁶ = 2809717 is a prime.

It is a super-2 number, since 2×2809781² = 15789738535922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2809783) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10805 + ... + 11061.

It is an arithmetic number, because the mean of its divisors is an integer number (262171).

2^2809781 is an apocalyptic number.

It is an amenable number.

2809781 is a deficient number, since it is larger than the sum of its proper divisors (336271).

2809781 is a wasteful number, since it uses less digits than its factorization.

2809781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328 (or 299 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 2809781 is about 1676.2401379277. The cubic root of 2809781 is about 141.1099020754.

The spelling of 2809781 in words is "two million, eight hundred nine thousand, seven hundred eighty-one".