12978781 has 4 divisors (see below), whose sum is σ = 13124700. Its totient is φ = 12832864.

The previous prime is 12978773. The next prime is 12978809. The reversal of 12978781 is 18787921.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1863225 + 11115556 = 1365^2 + 3334^2 .

It is a cyclic number.

It is not a de Polignac number, because 12978781 - 2³ = 12978773 is a prime.

It is a super-2 number, since 2×12978781² = 336897512491922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12978731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 72826 + ... + 73003.

It is an arithmetic number, because the mean of its divisors is an integer number (3281175).

Almost surely, 2^12978781 is an apocalyptic number.

It is an amenable number.

12978781 is a deficient number, since it is larger than the sum of its proper divisors (145919).

12978781 is an equidigital number, since it uses as much as digits as its factorization.

12978781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145918.

The product of its digits is 56448, while the sum is 43.

The square root of 12978781 is about 3602.6075278887. The cubic root of 12978781 is about 235.0054684105.

The spelling of 12978781 in words is "twelve million, nine hundred seventy-eight thousand, seven hundred eighty-one".