12781009 has 2 divisors, whose sum is σ = 12781010. Its totient is φ = 12781008.

The previous prime is 12781007. The next prime is 12781049. The reversal of 12781009 is 90018721.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9641025 + 3139984 = 3105^2 + 1772^2 .

It is a cyclic number.

It is not a de Polignac number, because 12781009 - 2¹ = 12781007 is a prime.

Together with 12781007, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (12781007) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6390504 + 6390505.

It is an arithmetic number, because the mean of its divisors is an integer number (6390505).

Almost surely, 2^12781009 is an apocalyptic number.

It is an amenable number.

12781009 is a deficient number, since it is larger than the sum of its proper divisors (1).

12781009 is an equidigital number, since it uses as much as digits as its factorization.

12781009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 12781009 is about 3575.0537058903. The cubic root of 12781009 is about 233.8056742522.

The spelling of 12781009 in words is "twelve million, seven hundred eighty-one thousand, nine".