2787781 has 2 divisors, whose sum is σ = 2787782. Its totient is φ = 2787780.

The previous prime is 2787769. The next prime is 2787859. The reversal of 2787781 is 1877872.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1846881 + 940900 = 1359^2 + 970^2 .

It is a cyclic number.

It is not a de Polignac number, because 2787781 - 2⁵ = 2787749 is a prime.

It is a super-2 number, since 2×2787781² = 15543445807922, which contains 22 as substring.

It is a Chen prime.

2787781 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2787751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1393890 + 1393891.

It is an arithmetic number, because the mean of its divisors is an integer number (1393891).

2^2787781 is an apocalyptic number.

It is an amenable number.

2787781 is a deficient number, since it is larger than the sum of its proper divisors (1).

2787781 is an equidigital number, since it uses as much as digits as its factorization.

2787781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 43904, while the sum is 40.

The square root of 2787781 is about 1669.6649364468. The cubic root of 2787781 is about 140.7406496212.

Subtracting from 2787781 its reverse (1877872), we obtain a palindrome (909909).

The spelling of 2787781 in words is "two million, seven hundred eighty-seven thousand, seven hundred eighty-one".