2800781 has 2 divisors, whose sum is σ = 2800782. Its totient is φ = 2800780.

The previous prime is 2800769. The next prime is 2800783. The reversal of 2800781 is 1870082.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2788900 + 11881 = 1670^2 + 109^2 .

It is a cyclic number.

It is not a de Polignac number, because 2800781 - 2¹⁰ = 2799757 is a prime.

It is a super-2 number, since 2×2800781² = 15688748419922, which contains 22 as substring.

Together with 2800783, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2800781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2800783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1400390 + 1400391.

It is an arithmetic number, because the mean of its divisors is an integer number (1400391).

2^2800781 is an apocalyptic number.

It is an amenable number.

2800781 is a deficient number, since it is larger than the sum of its proper divisors (1).

2800781 is an equidigital number, since it uses as much as digits as its factorization.

2800781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 896, while the sum is 26.

The square root of 2800781 is about 1673.5534051831. The cubic root of 2800781 is about 140.9590780429.

The spelling of 2800781 in words is "two million, eight hundred thousand, seven hundred eighty-one".