12787781 has 2 divisors, whose sum is σ = 12787782. Its totient is φ = 12787780.

The previous prime is 12787763. The next prime is 12787783. The reversal of 12787781 is 18778721.

12787781 is digitally balanced in base 3, 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., 7474756 + 5313025 = 2734^2 + 2305^2 .

It is a cyclic number.

It is not a de Polignac number, because 12787781 - 2¹⁸ = 12525637 is a prime.

It is a super-2 number, since 2×12787781² = 327054685807922, which contains 22 as substring.

Together with 12787783, 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 (12787783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6393890 + 6393891.

It is an arithmetic number, because the mean of its divisors is an integer number (6393891).

Almost surely, 2^12787781 is an apocalyptic number.

It is an amenable number.

12787781 is a deficient number, since it is larger than the sum of its proper divisors (1).

12787781 is an equidigital number, since it uses as much as digits as its factorization.

12787781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 43904, while the sum is 41.

The square root of 12787781 is about 3576.0006991051. Note that the first 3 decimals coincide. The cubic root of 12787781 is about 233.8469608326.

The spelling of 12787781 in words is "twelve million, seven hundred eighty-seven thousand, seven hundred eighty-one".